GEOSCIENCE CANADA Volume 39 2012 77

PAUL F. HOFFMAN SERIES

capped by platformal carbonate after la formation locale d’un relief the establishment of a NNW-facing topographique et une prisme des stromatolitic reef complex that formed strates. Ces dernières ont finalement at the same time as reefs in the Little été recouvertes de carbonates de plate- Dal Group of the Mackenzie Moun- forme issus de la mise en place d’un tains, Northwest Territories. Correla- complexe récifal stromatolitique tions between specific formations exposé NNW contigu à la formation within these groups and with equiva- de même âge du groupe Little Dal des lent strata in the Shaler Supergroup on montagnes Ogilvie, en Territoires du Victoria Island are tested with carbon Nord-Ouest. Les corrélations existant isotope chemostratigraphy. The basin- entre des formations spécifiques de forming event that accommodated chacun de ces groupes, sont testées Early Neoproterozoic Basin these strata was restricted to north- grâce à la chimiostratigraphie des iso- Formation in Yukon, western Laurentia (present day coordi- topes du carbone. De ce fait, cet Canada: Implications for nates) and does not represent wide- événement ne correspond pas au large spread rifting of the entire western rifting s’étendant sur l’entière bordure the make-up and break-up margin. Instead we propose that these ouest de la Laurentie et nous pro- of Rodinia strata were accommodated by exten- posons à la place, que ces strates ont sion and localized subsidence associat- été localisées au cours d’un rift avorté ed with the passing of Rodinia over a généré par la mise en place simultanée Francis A. Macdonald1*, Galen P. plume and the emplacement of the des larges provinces ignées Guibei Halverson2, Justin V. Strauss1, Emily coeval Guibei (China) and Gairdner (Chine) et Gairdner (Australie). La bor- F. Smith1, Grant Cox2, Erik A. (Australia) large igneous provinces. dure nord de la Laurentie a été réac- Sperling1, Charles F. Roots3 1 Deposition culminated with the intru- tivée par une nouvelle phase d’exten- Department of Earth and Planetary sion of the Gunbarrel dykes. The sion à ca. 720 Ma associée à l’emplace- Sciences, Harvard University, 20, Oxford northern margin of Laurentia was ment de la province ignée Franklin. St., Cambridge, MA 02138, U.S.A. 2 reactivated by renewed extension at ca. L’amincissement crustal et la formation Department of Earth and Planetary 720 Ma associated with the emplace- d’une marge passive thermiquement Sciences, McGill University, Montreal, QC, ment of the Franklin large igneous subsidente le long de la bordure ouest Canada province. Significant crustal thinning de la Laurentie ne se sont certainement 3 Geological Survey of Canada, Whitehorse, and generation of a thermally subsid- pas produits avant l’Édiacarien supé- YT, YIA 1B5, Canada ing passive margin on the western mar- rieur. *[email protected] gin of Laurentia may not have occurred until the late Ediacaran. INTRODUCTION SUMMARY The supercontinent Rodinia was origi- Geological mapping and stratigraphic RÉSUMÉ nally conceived on the basis of 1.2–1.0 analysis of the early Neoproterozoic Le cartographiage géologique et Ga orogenesis on several continents Fifteenmile Group in the western l’analyse stratigraphique du groupe and Neoproterozoic–Cambrian-age Ogilvie Mountains of Yukon, Canada, néoprotézoïque Fifteenmile situé à rifting and development of passive have revealed large lateral facies l’ouest des montagnes Ogilvie du margins surrounding Laurentia (Bond changes in both carbonate and silici- Yukon, Canada, ont révélé de grands and Kominz 1984; Dalziel 1991; Hoff- clastic strata. Syn-sedimentary NNW- changements latéraux de faciès à la fois man 1991; Moores 1991). However, side-down normal faulting, during dep- pour les strates carbonatées et silico- the exact arrangement of cratons, the osition of the lower Fifteenmile clastiques. La mise en place des failles timing and geometry of break-up, the Group, generated local topographic normales syn-sédimentaires inclinées number of rifting events, and the rela- relief and wedge-shaped stratal geome- vers le NNW au cours du dépôt du tionship to large igneous provinces tries. These strata were eventually groupe Fifteenmile inférieur, a entrainé (LIPs) have remained controversial 78

(e.g. Hoffman 1991; Moores 1991; Dalziel 1997; Sears and Price 2003; Goodge et al. 2008; Li et al. 2008b; Evans 2009). The construction of an accurate Rodinian paleogeography and understanding the chronology of breakup is essential for testing pro- posed links between Neoproterozoic tectonics, climate, and biogeochemistry. For example, enhanced weatherability and CO2 consumption during the break-up of Rodinia has been pro- posed as the background condition for the cooling trend that culminated in Cryogenian glaciation and Snowball Earth (Kirschvink 1992; Hoffman et al. 1998; Hoffman and Schrag 2002; Schrag et al. 2002; Godderis et al. 2003; Donnadieu et al. 2004). Paleogeographic reconstruc- tions place Laurentia in the core of Rodinia (e.g. Li et al. 2008b). Multiple extensional events attributed to rifting of the western margin of Laurentia Figure 1. Distribution of Proterozoic strata in the Ogilvie, Wernecke, and Macken- (present coordinates) have been previ- zie mountains of NW Canada, modified from Abbott (1997). ously identified in the Windermere Supergroup (~0.78–0.54 Ga, Sequence suite of NE–SW oriented transfer Based on these data, we propose new C of Young et al. 1979), including at faults in the Katherine and Little Dal correlations for Sequence B strata least one in the ca. 780–660 Ma Coates groups based on abrupt lithofacies and between Yukon and Northwest Terri- Lake and Rapitan groups in the north- thickness variations and suggested that tories and a new model for the tectonic ern Cordillera (Jefferson and Parrish the MMSG was accommodated by evolution of northwestern Laurentia 1989; Mustard 1991; Lund et al. 2003; SW–NE extension on the western from the formation to the break-up of Macdonald et al. 2010b), and another margin of Laurentia. This model the supercontinent Rodinia. in the ca. 580–560 Ma Hamill-Gog invoked a simple shear, upper Group in the southern Cordillera (Col- plate–lower plate detachment geometry GEOLOGICAL BACKGROUND pron et al. 2002). However, earlier and (Lister et al. 1986) previously devel- Tectonic Setting poorly understood early Neoprotero- oped for the early Paleozoic passive Proterozoic strata in the northwestern zoic basin forming events (Sequence B margin, where margin-orthogonal Canadian Cordillera are preserved in of Young et al. 1979) are also required transfer faults were proposed (Cecile et erosional windows separated by 40–80 to accommodate the Pinguicula and al. 1997). Although strong lineaments km of Phanerozoic cover (termed Fifteenmile groups of the Yukon and are present in the Ediacaran to early ‘inliers’; Fig. 1). The inliers of the the equivalent Mackenzie Mountains Paleozoic Selwyn Basin (Cecile et al. Ogilvie Mountains are situated on the Supergroup (MMSG) in the Mackenzie 1997), their involvement in an earlier ‘Yukon block’ (Jeletsky 1962), which is Mountains and Shaler Supergroup on extension is speculative. None of the an isostatically independent crustal Victoria Island (Figs. 1 and 2). Aitken proposed early Neoproterozoic trans- block separated on its eastern margin (1981) documented facies patterns in fer faults were identified in surface from the North American autochthon the Little Dal Group of the MMSG exposures in the Mackenzie Mountains by the Cretaceous to Paleogene that suggested a NNW-facing margin, (Turner and Long 2008). Richardson Fault Array (Norris 1997; including a stromatolitic buttress in the Early Neoproterozoic strata in Hall and Cook 1998). This Platform Assemblage that faces the the Yukon and Alaska have been large- NNW–SSE zone of crustal weakness Basinal Assemblage to the NNW. Cit- ly overlooked in tectonic models of roughly outlines large Paleozoic facies ing the lack of syn-sedimentary fault- basin development. Here we present changes that define the Richardson ing, obvious syn-rift deposits and the the first detailed stratigraphic descrip- Trough (Cecile 1982, 2000; Cecile et al. continuity of early Neoproterozoic tion of the Fifteenmile Group in the 1997), large Neoproterozoic facies sequences between the Mackenzie Coal Creek inlier of Yukon, Canada. changes in the Windermere and Mountains and Victoria Island, Rain- We further complement these strati- Mackenzie Mountains Supergroups bird et al. (1996) proposed that graphic descriptions with new geologi- (Eisbacher 1981; Norris 1997), and the Sequence B strata were deposited in an cal mapping (Fig. 3), and detailed car- easternmost extent of exposure of the intracratonic sag basin. Alternatively, bon isotope chemostratigraphy Pinguicula Group and Wernecke Turner and Long (2008) inferred a through large lateral facies changes. Supergroup (Delaney 1981; Eisbacher GEOSCIENCE CANADA Volume 39 2012 79

Figure 2. Proposed lithostratigraphic correlation of Neoproterozoic strata between the different Proterozoic inliers of the Ogilvie Mountains, the Wernecke/Mackenzie Mountains, and Victoria Island. Stratigraphy of the Wernecke and Mackenzie Mountains adapted from Turner (2010) and stratigraphy of Victoria Island adapted from Long et al. (2009). Microfossil assem- blages of the lower Wynniatt Formation (Wynniatt assemblage) and Rusty Shale formation (Rusty assemblage) are described by Butterfield (2005a, b) and Butterfield and Rainbird (1998). Scale microfossils from the Fifteenmile Group (formerly assigned to the Tindir Group) are described by Cohen et al. (2011) and Cohen and Knoll (2012). Age constraints are discussed in text.

1981). To the east of the Richardson tains fold belt (Aitken and Long 1978; to Paleogene Dawson Fault, which sep- Fault Array, Neoproterozoic rocks out- Park et al. 1989). The Yukon block is arates it from the Selwyn Basin crop in the arcuate Mackenzie Moun- bound to the south by the Cretaceous (Gordey and Anderson 1993), and to 80 Geology of the Coal Creek inlier of map of the authors with contributions from 1:50 000 mapped by Ogilvie Mountains, the southwest Thompson Figure 3. et al. (1994). GEOSCIENCE CANADA Volume 39 2012 81 the north and west by the Cenozoic The Wernecke Supergroup corre- correlation with the pre-1270 Ma Dis- Kaltag Fault (Fig. 1). Early Neopro- sponds to Sequence A of Young et al. mal Lake Group in the Coppermine terozoic strata equivalent to the plat- (1979, 1981) and consists of over 10 homocline (Kerans et al. 1981; formal rocks exposed in the inliers km of polydeformed carbonate and Thorkelson et al. 2005). This correla- have not been identified south of the siliciclastic rocks (Delaney 1981). The tion stemmed from the identification Dawson Fault (Abbott 1997). Abrupt Wernecke Supergroup was previously of a dyke assigned to the ca. 1380 Ma facies changes occur across the Daw- considered to be pre-1.71 Ga (Thorkel- Hart River Sills that cuts fine-grained son Fault in late Neoproterozoic and son et al. 2005); however, this con- clastic strata assigned to Pinguicula A Paleozoic strata, suggesting that it was straint has become ambiguous follow- in the Wernecke Mountains (Thorkel- also a long-lived basement structure ing the new geochronological data of son 2000). However, the intruded stra- that originated during the Proterozoic Furlanetto et al. (2009) which include ta were later reassigned to the Wer- and was sporadically reactivated in the ca. 1.65 Ga zircons in the Fairchild necke Supergroup (Medig et al. 2010), Phanerozoic (Thompson et al. 1987; Lake, Quartet, and Gillespie Lake which raised the possibility that Pin- Abbott 1997; Norris 1997). groups. Thus, it appears that the Wer- guicula A–C is younger than 1270 Ma. necke Supergroup was deposited in a The Pinguicula Group is Stratigraphic Setting syn-tectonic basin immediately prior to unconformably overlain by the MMSG. Since the early recognition that similar the ca. 1.60 Ga Racklan orogeny and The MMSG correlates with the Shaler stratigraphic sequences were exposed emplacement of the mineralized Wer- Supergroup on Victoria Island at a for- throughout NW Canada (Fig. 2; necke breccia (Thorkelson et al. 2001a, mation resolution (Rainbird et al. 1996; Gabrielse 1972; Young 1977, 1981; 2005). Mafic intrusions cutting the Jones et al. 2010), and as mentioned Young et al. 1979), correlation of units Wernecke Supergroup are likely correl- above, a portion of the of the MMSG between the Tatonduk (Young 1982), ative with the ~1380 Ma Hart River can be correlated across the Richard- Coal Creek (Thompson et al.,1987), sills in the Hart River inlier (Abbott son Fault Array into eastern Yukon Hart River (Abbott 1997), and Wer- 1997) or the ~1270 Ma Bear River (Turner 2011), however, how these necke (Eisbacher 1981; Delaney 1981) dykes (Thorkelson 2000; Schwab et al. strata extend to inliers in the Ogilvie inliers of the Ogilvie and Wernecke 2004). Mountains has remained uncertain. Mountains of Yukon (Eisbacher 1981; The Wernecke Supergroup is Age constraints on the lower MMSG Thorkelson 2000; Thorkelson et al. unconformably overlain by the Pin- and its equivalents (Fig. 2) are provided 2005), the Mackenzie Mountains fold guicula Group, which was originally by 1050±5 and 1059±3 Ma detrital zir- belt of the Northwest Territories included with Sequence B strata of cons from unit PD1 and 1001±2 Ma (NWT) (Aitken 1981), and the Amund- northwest Canada and thought to be detrital zircons from unit PD3 of the sen Basin of Nunavut and NWT equivalent with part of the lower Hart River inlier (both units are (Young 1981; Rainbird et al. 1996) has MMSG (Young et al. 1979; Aitken and assigned to the lower Fifteenmile been a principal goal in geological McMechan 1991; Rainbird et al. 1996). Group), a 1079 ±2 Ma detrital zircon mapping and stratigraphic analysis. The Pinguicula Group was originally in unit K7 of the Katherine Group of Recent mapping and stratigraphic, geo- defined in the Wernecke Mountains the Mackenzie Mountains, and a chemical, and geochronological analy- near Pinguicula Lake and separated 1077±2 Ma detrital zircon from the ses (Turner and Long 2008; Furlanetto into units A–F (Eisbacher 1981). Nelson Head Formation of Victoria et al. 2009; Jones et al. 2010; Macdon- Abbott (1997) later described early Island (Rainbird et al. 1997). An addi- ald and Roots 2010; Macdonald et al. Neoproterozoic strata in the Hart tional upper age constraint is given by 2010b, 2011; Medig et al. 2010; River inlier of the eastern Ogilvie the ca. 780 Ma mafic intrusions Martell et al 2011; Turner 2011; Mountains that rested with an angular (assigned to the Gunbarrel igneous Halverson et al. 2012) have resulted in unconformity on the Gillespie Lake event) that cut the Little Dal Group up important new constraints on these Group and Hart River sills and were to the Gypsum Formation ( Jefferson successions. However, a comprehen- overlain by the Callison Lake dolo- and Parrish 1989; Harlan et al. 2003). sive regional synthesis of Proterozoic stone. He correlated these strata with These intrusions have been correlated stratigraphy has remained elusive due units A–D of the Pinguicula Group in geochemically with the Little Dal to the scarcity of isotopically dateable the Wernecke Mountains, but recog- Basalt (Dudás and Lustwerk 1997), rock types, significant along-strike nized an angular unconformity which separate the upper MMSG from facies changes, poorly understood between units C and D. Refining earlier the unconformably overlying Coates structural complications between work in the Wernecke Mountains, Lake Group and the Cryogenian–Edi- inliers, and the lack of detailed descrip- Thorkelson (2000) upheld units A–C in acaran Windermere Supergroup tions of Proterozoic stratigraphy the Pinguicula Group, but reassigned (Sequence C of Young et al. 1979). exposed in Yukon. units D–F to the Hematite Creek No crystalline basement is Group. Turner (2011) subdivided the STRATIGRAPHY OF THE COAL exposed in the Ogilvie, Wernecke, or Hematite Creek Group and reassigned CREEK INLIER Mackenzie mountains. The oldest the uppermost units to the Katherine Previous Studies exposed rocks belong to the Paleopro- and Little Dal groups of the MMSG. Neoproterozoic strata in the Coal terozoic Wernecke Supergroup, which The more restricted definition of units Creek inlier were originally separated is only present on the Yukon block. A–C of the Pinguicula Group permits from the Wernecke Supergroup by 82

Norris (1978) and later mapped and quently subdivided the lower assem- in the Coal Creek inlier. described as the Fifteenmile Group blage into the informal Gibben and (named after the headwaters of Fif- Chandindu formations and the overly- Pinguicula Group teenmile River; Thompson et al. 1987, ing Reefal assemblage. Macdonald et al. In the Coal Creek inlier, the Pinguicula 1994) and the Mount Harper Group (2011) also revised the stratigraphic Group is exposed in a syncline to the (Mustard and Roots 1997). The Fif- nomenclature by removing the Callison NW of Mt. Gibben (Fig. 3, section teenmile Group was a provisional term Lake dolostone (Abbott 1997; Mac- E1003) and along ridges north of used to distinguish older Neoprotero- donald and Roots 2010) from the Fif- Mount Harper, where it uncon- zoic strata in the Coal Creek inlier teenmile Group. The Callison Lake formably overlies the Wernecke Super- from the Lower Tindir Group of the dolostone is overlain by the Mount group. The Pinguicula Group has Tatonduk inlier and the Pinguicula Harper Group, which includes the been divided into a siliciclastic-domi- Group in the Wernecke Mountains lower Mount Harper Group (LMHG) nated unit and a carbonate-dominated (Thompson et al. 1994). The Fifteen- and the Mount Harper volcanic com- unit, referred to as Pinguicula A and mile Group was originally subdivided plex (MHVC; Macdonald et al. 2011; Pinguicula B/C, respectively (Macdon- into upper and lower subgroups, con- Fig. 2). A minimum age constraint on ald et al. 2011). On the north limb of taining three (PF1–PF3) and five the Fifteenmile Group comes from the syncline near Mt. Gibben, Pinguic- (PR1–PR5) informally defined map rhyolite flows in the upper MHVC, ula A is composed of a lower ~320 m- units, respectively (these units are which were dated at 717.43 ± 0.14 Ma thick unit of weakly foliated, brown to shown on the regional map of (U/Pb ID-TIMS; Macdonald et al. grey-coloured siltstone and shale with Thompson et al. (1994); see Figure 11 2010a). The MHVC is interbedded irregularly dispersed large dolostone of Macdonald et al. (2011) for a chart with and conformably succeeded by blocks and conglomerates interpreted comparing the old and new strati- 716.47 ± 0.24 Ma glacial deposits of as olistostromes (Fig. 4a) and debris graphic nomenclature). Previous the Rapitan Group (U/Pb ID-TIMS; flows, respectively (Macdonald et al. workers suggested that the lower Fif- Macdonald et al. 2010a). In the Coal 2011). On the south limb of the syn- teenmile Group was intruded by brec- Creek inlier, the Rapitan Group is cline, the distinct orange-coloured cia (referred to as the ‘Ogilvie breccia’) overlain by the Cryogenian Hay Creek dolostone blocks are over 10 m in equivalent to the ca. 1600 Ma Wer- Group and the Ediacaran to Early diameter and their internal bedding is necke breccia (Thorkelson et al. 2001b) Cambrian ‘Upper’ Group (Macdonald discordant with the surrounding silici- and hence was partly equivalent to the et al. 2011; Chapter 3.3.4 in Martel et clastic matrix. The olistostrome-bear- Pinguicula Group and Wernecke al. 2011), which are in turn uncon- ing siliciclastic rocks are overlain by Supergroup of the Wernecke inlier formably overlain by the Cambrian to >500 m of yellow to blue-grey weath- (Thompson et al., 1987, 1994). How- Devonian Bouvette Formation. ering dolostone of Pinguicula B/C. ever, Medig et al. (2010) demonstrated On the north side of the syncline, the that map unit PR1 overlies a regolith Methods carbonate rocks consist predominantly formed on top of the Ogilvie breccia We measured 54 stratigraphic sections of grainstone and stromatolites (a and that all of the lower Fifteenmile through the Pinguicula, Fifteenmile, facies characteristic of Pinguicula C in Group is younger. Moreover, a tuff Mount Harper, Rapitan, Hay Creek, the Hart River and Wernecke inliers), recovered within strata previously and ‘Upper’ groups in the Coal Creek whereas on the south side of the syn- mapped as PR4 (revised to PF1a to inlier. Carbonate lithofacies are cline the dolostones are characterized reconcile inconsistencies of previous defined (Table 1) and used in the by laminated dolomicrite and mapping) was dated at 811.51 ± 0.25 lithostratigraphic descriptions below dolosparite with rare lime mudstone (a Ma (U/Pb ID-TIMS; Macdonald and along with siliciclastic lithofacies differ- facies characteristic of Pinguicula B in Roots 2010; Macdonald et al. 2010a). entiated by grain size and composition. the Hart River and Wernecke inliers). We follow Medig et al.’s (2010) sugges- These lithofacies are then grouped into These facies are gradational in the Coal tion that units PR1–PR3 are largely facies assemblages (Table 2), which are Creek inlier; hence we mapped them correlative with units A–C of the Pin- used to track the evolving depositional together and refer to this sequence as guicula Group, which provides a dis- environments and sequence architec- Pinguicula B/C because they represent tinct separation of the remaining Fif- ture of the Fifteenmile Group. one depositional package with distinct teenmile Group from the underlying Sequences described are composed of lateral facies changes. At the top of Pinguicula Group. parasequence sets that define systems Pinguicula B/C, stromatolites with Major revisions to the map- tracts (Mitchum and Van Wagoner high synoptic relief are overlain with ping in the Coal Creek inlier, including 1991), but without further age con- black shale and minor dolomicrite, and elimination of many inferred thrust straints, the order of these sequences green-weathering flat-laminated silt- faults in the lower Fifteenmile Group, remains uncertain. In the descriptions stone, which we include with Pinguicu- led Macdonald et al. (2011) to propose below we focus on the Fifteenmile la B/C. a new subdivision of the Fifteenmile Group, but to provide broader North of Mount Harper (Fig. Group into an informal ‘lower assem- tectonostratigraphic context we also 3; section G135), the Pinguicula Group blage’ of mixed shale and dolostone, discuss the bounding stratigraphy in is represented by a thick dolostone overlain by the informal Craggy dolo- the Pinguicula Group, Callison Lake capped by a spectacular assemblage of stone. Halverson et al. (2012) subse- dolostone, and Mount Harper Group Minjaria, Tungussia, and Conophyton stro- GEOSCIENCE CANADA Volume 39 2012 83

Table 1. Carbonate lithofacies and descriptions of lithology, bedding, and sedimentary structures that distinguish these facies.

Carbonate Lithofacies Lithology Bedding Comments

Rhythmite “Micrite, mostly limestone, “Flat-bedded, parallel-laminated, “Commonly associated minor dolostone” <10 cm-thick, commonly graded” with shale, marl, and debris flows”

Ribbonite Micrite to grainstone Wavy laminated with or without “Molar tooth structure wave or current ripples or low- common in fetid, angle cross-lamination; commonly organic-rich facies” nodular; 20 cm-thick

Stromatolite Undulose and crinkly to “Discrete columnar to rounded Commonly associated fenestral laminated dolostone microbialite with >1 cm of synoptic with edgewise relief, massive weathering bioherms conglomerate and (m-scale) and reefs (100 m-scale)” grainstone

Grainstone “Well-sorted sand to “With or without large-scale Recrystallization packestone, oolitic or cross-bedding, massively bedded commonly limits intraclastic dolostone” >0.2 m thick, coarsely confident determination recrystalized” of original grainsize

Microbialaminite Undulose and crinkly to Thin to massive beds “Commonly associated fenestral laminated dolostone with shale and rhythmite, or limestone or with itraclast breccia and rip-up clasts”

Intraclast breccia “Poorly sorted gravel to “Massive, resistant, upward buckling Associated with boulder clasts with void-fill teepee structures and karstic microbialminite and cement, angular to dissolution surfaces are common” grainstone subrounded; silicified dolostone”

Debris flow breccia “Gravel to boulder, angular to Graded and imbricated Commonly associated subrounded, tabular clasts in with rhythmite or shale; micrite to grainstone matrix” includes massive olistoliths matolites (Halverson et al. 2012). The Reefal assemblage and Craggy dolo- thinning wedge of the Pinguicula stromatolitic dolostone in this section stone, which constitute the upper Fif- Group. Locally, the basal Gibben for- is overlain by green siltstone. The Pin- teenmile Group (Macdonald et al. mation includes a thin medium-grained guicula Group tapers out to the NW of 2011; Halverson et al. 2012). Because sandstone unit with abundant carbon- section G135 by a combination of of large lateral facies change within the ate and slate lithic clasts. It is succeed- onlap onto the unconformably under- Fifteenmile Group, we use a sequence ed by a shoaling-upward interval of lying Gillespie Lake Group (upper stratigraphic approach to attempt the grey dolomitic ribbonite and wacke- Wernecke Supergroup) and truncation correlation of time-equivalent surfaces stone that grade into oolitic grainstone beneath an erosional unconformity at across the basin and help interpret the and eventually into microbialaminite the base of the Fifteenmile Group basin fill. Where subaerial unconformi- with tepee structures (see Table 1 for (section G130, Fig. 3). ties are apparent, depositional descriptions of lithofacies). Here the sequences are defined. Elsewhere, par- top of the formation is interpreted to ticularly in more distal environments, be a subaerial exposure surface with Fifteenmile Group the maximum regressive surface (MRS) evidence of minor karsting. It is over- The Fifteenmile Group is exposed in is used as the correlative sequence lain by maroon, mud-cracked shale and the Tatonduk, Coal Creek, and Hart boundary. siltstone of the basal Chandindu for- River inliers. We recently proposed a mation. revised subdivision of the Fifteenmile Gibben Formation Near Mt. Gibben (E1002; Group into four informally defined Lithostratigraphy Figs. 3 and 5), the basal sandstone is formations: the Gibben and Chandin- North of Mt. Harper (section G130; missing and the lowermost Gibben du formations, which constitute the Figs. 3 and 5), the Gibben formation formation consists of a basal ~100 m lower Fifteenmile Group, and the unconformably overlies a westward- interval of blue-grey oolitic and stro- 84

Table 2. Facies assemblages and descriptions of lithofacies associations, sedimentary structures, and their potential depositional environments.

Assemblage Lithofacies Associations Sedimentary Structures Depositional environments

FA1: Carbonate Platform / “Microbialaminite, grainstone, “Teepee structures, beach-rock, Periodically restricted and Tidal Flats intraclast breccia” pervasive void-fill cements, exposed intertidal to ooils, edgewise conglomerate” supratidal lagoon

FA2: Back Reef Lagoon “Microbialaminite, grainstone, “Pin-stripe laminated Restricted lagoon adjascent ribbonite, rhythmite, shale” microbialite and mudstone with to stromatolite reef no scours, red, terestrial siltstone”

FA3: Rim / Reef Core “Stromatolite, talus breccia” Massively recrystalized Protective stromatolite reef

FA4: Upper Foreslope “Ribbonite, rhythmite, siltstone, “Hummocky cross-lamination, Upper foreslope with shale, stromatolite bioherms” slumps, graded beds, olistoliths, longshore flow outboard of molar tooth structure common a carbonate reef or platform in fetid lime mudstone”

FA5: Lower Foreslope “Shale, siltstone” “Graded beds, flat lamination, Lower foreslope outboard of occasional channelization” significant carbonate deposition

FA6: Pro-delta “Shale, siltstone, sandstone, “Mudcracks, channels, large River delta with continental rounded to sub-rounded cross-bed sets” source or alluvial fan conglomerate” adjacent to active fault matolitic dolostone that is faulted River inlier defined by Abbott (1997) an additional unconformity is present against sheared and chloritized sills. In that was subsequently revised to the at this level. Up-section, the mud- the northernmost exposures of the Fifteenmile Group based on the con- cracked interval transitions into cyclic Coal Creek inlier (section E1001), the formable contact at the top of the packages of shale, siltstone, and dolo- Gibben formation thickens dramatical- sandstone (Medig et al. 2010; Halver- stone that are typically capped by ly, with up to several hundred metres son et al. 2012). In the Hart River inli- grainstone, stromatolites, or micro- of grey to black shale that transitions er, PD1 comprises a series of shale to bialaminite. However, the upper up-section into muddy pink limestone sandstone cycles that broadly make up Chandindu formation is overall quite ribbonite. This pink limestone is fol- a single depositional sequence (S1, not variable between sections, which we lowed by oolitic and microbialaminite shown here; see Halverson et al. 2012). attribute to differential subsidence facies of dolostone, typical of the Above the sandstone, the remainder of associated with protracted tectonic upper Gibben formation in other sec- the Gibben formation spans a second extension. This syn-Chandindu faulting tions. The thick lower shale and pink depositional sequence (S2; Fig. 5 and is apparent from map relations (Fig. 3) limestones decrease in thickness lateral- 6), which consists of a shale to carbon- and the presence of large olistoliths ly (Fig. 6), disappearing altogether in ate highstand (regressive) systems tract within the upper part of the formation many sections where the Gibben for- bound by a subaerial unconformity (Fig 4b). In some stratigraphic sec- mation is represented by only a rela- that marks the contact with the overly- tions, stromatolitic bioherms are rela- tively thin interval of dolomitic micro- ing Chandindu formation. tively abundant, as are poorly sorted bialaminites (Fig. 6). The result is that and massive coarse-grained sandstone the total thickness of the Gibben for- Chandindu Formation beds. The upper boundary of the mation varies from <20 to >600 m as Lithostratigraphy Chandindu formation is marked by a a result of expansion of the section The top of the Gibben formation major flooding surface, which effec- into fault-bound graben and condensa- marks an abrupt transition from nearly tively separates this heterogeneous tion on topographic highs. pure carbonate sediment into an inter- sequence from the overlying shale- and val of maroon shale and siltstone with dolomite-dominated Reefal assemblage. Sequence Stratigraphy abundant mud-cracks, characteristic of In the Coal Creek inlier, the Gibben the basal Chandindu formation. The Sequence Stratigraphy formation contains a thin, basal quartz- Gibben formation thins laterally and is The basal mud-cracked interval of the lithic arenite. The sandstone correlates in places absent under this distinctive Chandindu formation records one of with the PD1 map unit in the Hart mud-cracked interval, suggesting that few, well-developed lowstand systems GEOSCIENCE CANADA Volume 39 2012 85

Figure 4. Olistoliths and slumps in Neoproterozoic strata of the Coal Creek inlier. A) Large carbonate olistostromes of the Gillespie Lake Group (outlined in white) in siltstone of unit A of the Pinguicula Group, looking north, just west of J1020 (Fig. 3). B) Olistostrome containing the contact between the Gibben and Chandindu formations (outlined in white) within the lower Chandindu formation near F1018 (Fig. 3). Note that this olistolith is near the large normal fault shown in Figure 7a that was active during deposition. C) Slump fold (outlined in white) on the hanging-wall of the syn-Chandindu fault shown in Figure 7a, just west of section F1018. This fold is verging to the NW, into the axis of the basin and away from the footwall. D) Olistolith within sequence S3a of the Reefal assemblage (outlined in white), just west of section G022 (Fig. 3). tracts (LST) in the lower Fifteenmile nated at the contact with the overlying form. Carbonate olistoliths and slump Group, marked by aggradational stacks Reefal assemblage. folding in the adjacent shale (Fig. 4d) of sandstone and conglomerate with suggests that significant relief existed abundant exposure surfaces, and is Reefal Assemblage on the flanks of stromatolitic build- interpreted to represent tidal-flat depo- Lithostratigraphy ups. We interpret large lateral facies sition as base level began to rise. The The Reefal assemblage consists of changes in the Reefal assemblage to overlying mud, silt, and wackes as well ~500 m of shale, siltstone, minor represent proximal platform and stro- as the shale–carbonate cycles are inter- coarse-grained sandstone, carbonate matolite reef facies in the SE to more preted to record a gradual increase in mudstone, grainstone, and massive distal foreslope and basin facies to the base level in sequence S3 (Figs. 5 and stromatolitic boundstone (Figs. 5 and NW (Tables 1 and 2). Sections from 6) and possibly represent the develop- 6), and is characterized by large lateral within the carbonate platform are ment of a deltaic system, through facies change. The NNW-side down dominated by stromatolitic bioherms which the gritty sands were delivered normal faults cut the Gibben and and intertidal to supratidal carbonate to the centre of the basin, and adjacent Chandindu formations, and are capped facies, including dark grey limestone to which, the tidally influenced by shale that marks the base of the microbialaminites (lagoonal), dolomitic shale–carbonate cycles formed. Nor- Reefal assemblage (Figs. 3, 6 and 7a). microbialaminites (supratidal), and mal faulting continued or resumed in Stromatolitic buildups were preferen- abundant grainstone (supratidal and the Chandindu formation, resulting in tially established on inferred paleo- proximal to the reef). To the NW, the local uplift and shedding of olistoliths highs along the footwalls of the faults, succession is dominated by shale and into the basin and flooding that culmi- marking the rim of the carbonate plat- gravitationally redeposited dolostone. 86

Figure 5. Lithostratigraphy, sequence stratigraphy, and carbon isotope chemostratigraphy of the Fifteenmile Group along an ESE–WNW transect of the southern belt of exposures, shown as A-A’ in Figure 3, which includes locations of the individual stratigraphic sections. Sequences S2-S7 are described in text.

Upper foreslope facies are dominated nal facies include shale, sandstone, and graphic repetition of lithologically sim- by carbonate mudstone, which com- re-sedimented carbonate. The complex ilar shale-to-carbonate sequences (Figs. monly contain molar tooth structure geometry of these facies assemblages 5 and 6) that was previously interpret- and massive talus breccias that shed results in significant variability between ed as the product of thrust faults (e.g. material from the adjacent reefs. Basi- measured sections and abundant strati- Thompson and Roots 1994). GEOSCIENCE CANADA Volume 39 2012 87

Figure 6. Lithostratigraphy, sequence stratigraphy, and carbon isotope chemostratigraphy of the Fifteenmile Group along an ESE–WNW transect of northern belt of exposures near Reefer Camp, shown as B-B’ in Figure 3, which includes locations of the individual stratigraphic sections. Sequences S2-S7 are described in text.

Sequence Stratigraphy Reefal assemblage on relict basement controlled sub-basins, carbonates are At the northwest end of the Coal highs, most prominently in sections found in the form of talus breccia, Creek inlier, measured sections of the F1018, G021, and G023 (‘Reefer slump breccia, grain flows, ribbonite, Reefal assemblage reveal symmetric Camp’). During the upper S3 HST turbidite, and rhythmite (Tables 1 and transgressive–regressive sequences and subsequent HSTs, the reef system 2). The ~811 Ma ash bed occurs capped by highstand stromatolitic prograded to the NNW, shedding car- between two carbonate sediment gravi- buildups (Fig. 7b). This architecture bonate debris into and eventually over- ty flows at the top of S6 (Fig. 5). reflects a series of NNW-prograding riding the adjacent shale sub-basin. Throughout the Reefal assem- stromatolite-cored reef tracts that These episodes of progradation are blage, sequences comprise coupled grade distally into grey and black shale- interrupted by abrupt flooding events TSTs and HSTs, with little or no clear dominated basinal deposits. The Reefal marking condensed transgressive sys- evidence of a significant base level fall. assemblage begins with the HST of tems tracts (TSTs), the most prominent A superb example of a well-preserved sequence S3 and contains four addi- of which (base S6) flooded most of TST–HST couplet occurs in sequence tional sequences (S4–S7) that can be the basin following progradation of S7b of section G021 (Fig. 6), in which correlated across the Coal Creek inlier. the stromatolite platform over much of the entire carbonate platform retro- Several of these are composite the basin at the top of S5. Only at the grades over a minor subaerial discon- sequence sets, which in some sections core of the reef system, in section formity developed in suptratidal micro- comprise 2 to 6 parasequences that are G023, are carbonates nearly continu- bialaminites (Fig 8). The maximum correlated with less confidence across ous. However, it is possible that depo- flooding surface (MFS) lies in red shale the basin (Figs. 5 and 6). The S3 HST sition may have been interrupted dur- just above a minor flooding unconfor- records the nucleation and growth of ing intermittent exposure of the plat- mity, which is superseded by red marly the first prominent reef system of the form. In the axes of the original fault- ribbonite, followed by stromatolites 88

Microbialaminite and low-relief stro- matolites (up to 10 cm of relief) are variably preserved through the perva- sive and multigenerational silicification and recrystallization. Ooids, coated grains, brecciated teepee structures, tabular clast conglomerates, intraclast breccia, and low-angle crossbeds have also been observed. Silicification is par- ticularly intense near the upper uncon- formity that separates the Craggy dolo- stone from the overlying Callison Lake dolostone. Although the pervasive sili- cification and recrystallization chal- lenge any comprehensive facies and sequence stratigraphic analyses of the Craggy dolostone, it is evident that it records the development of a broad and stable carbonate platform follow- ing the filling of residual sub-basin bathymetry in the Reefal assemblage.

Callison Lake Dolostone The Craggy dolostone is succeeded by the Callison Lake dolostone (Abbott 1997), which was recently separated from the Fifteenmile Group (Macdon- ald et al. 2011) because it uncon- formably overlies the Fifteenmile Group (Macdonald and Roots 2010). Halverson et al. (2012) suggested placement in the Mt. Harper Group, but we leave it as an orphaned unit here awaiting formal formation and group designation. Near Mt. Gibben, the Callison Lake dolostone is ~500 m thick and consists of a basal siltstone and shale sequence with laterally dis- continuous stromatolitic bioherms. This is overlain by medium-bedded Figure 7. A) Annotated photo looking west towards syn-Chandindu normal faults dolostone interbedded with black shale (in red) west of section F1018. Slump folding in Figure 4c and basinal facies of that consists almost exclusively of sedi- the Reefal assemblage are shown on hanging-wall. B) Annotated photo of reef mentary talc (Tosca et al. 2011). These core (outlined in white) of the Reefal assemblage, looking west from section F1018 strata (previously mapped as unit PF2; to the exposure directly below section G021. This photo is looking directly above Thompson et al. 1994) are overlain by the footwall shown in Figure 7a. Sequence stratigraphic systems tracts shown that ~200 m of a silicified dolostone char- are depicted in Figure 6. acterized by domal stromatolites (pre- viously mapped as unit PF3). An addi- tional ~25 m interval of interbedded and grainstone as the reef edge migrat- Craggy Dolostone black shale and dolostone occurs just ed back across the platform. The The uppermost sequence of the Reefal below the contact with the lower absence of falling stage and lowstand assemblage is capped by a distinct sub- Mount Harper Group. We map the systems tracts in the Reefal assemblage aerial exposure surface overlain by the entire shale–carbonate sequence as the is likely a result of broad and relatively heavily silicified and informally named Callison Lake dolostone because this rapid subsidence rates across the basin Craggy dolostone. The Craggy dolo- succession appears to form a genetical- that far outpaced any eustatic sea level stone forms a conspicuous, ridge- ly continuous unit, minimizes new ter- fluctuations (Mitchum and Van Wag- forming, >500-m-thick white dolo- minology and allows for straightfor- oner 1991). stone and consists predominantly of ward stratigraphic correlation between thick bedded and massively recrystal- the Coal Creek and Hart River inliers. lized and silicified sucrosic dolostone. GEOSCIENCE CANADA Volume 39 2012 89

Mount Harper Group Lower Mount Harper Group Conglomerate and breccia of the lower Mount Harper Group overlie the Calli- son Lake dolostone north of the Harper Fault and overlie the Wernecke Supergroup and an undifferentiated carbonate unit to the south (Fig. 3). Near Mount Harper, the lower Mount Harper Group is exposed on the north side of a syn-depositional fault scarp where it consists of up to 1100 m of talus breccia and debris flow conglom- erate interpreted as coalescing alluvial fans (Mustard and Donaldson 1990; Mustard 1991). To the east, in the Mt. Gibben area, the Lower Mount Harper Group is up to 300-m thick and con- sists predominantly of alluvial deposits commonly containing mud-cracks and conglomerate interbedded with minor marl that were deposited in a distal fan environment (Mustard 1991). The lower Mount Harper Group thins abruptly to the north away from the Harper Fault (Fig. 3).

Mount Harper Volcanic Complex The Mount Harper Volcanic Complex (MHVC) is divided into six informal units that are defined both stratigraphi- cally and compositionally (Roots 1987; Mustard and Roots 1997). A lower basaltic suite, composed of members A–C, comprises several hundreds of metres of pillowed and massive flows erupted into both subaqueous and sub- aerial settings. The lower flows overlie sandstone, siltstone, and cobble con- glomerate north of the Harper Fault (Mustard and Roots 1997). Soft-sedi- Figure 8. ment deformation, dolostone rip-ups, Sequence stratigraphic systems tracts outlined in red and reefs outlined and spiracles attest to the soft, damp in white; these are depicted in Figure 6 and described in text. A) Annotated photo of section G021, looking from the top peak shown in Figure 7b down the ridge to substrate encountered by the initial lava the south. Tents are circled in yellow for scale. B) Same exposure of section G021 flow (Mustard and Roots 1997). The as shown in Figure 8A, but looking east to show geometry of facies and systems basal flows on the south side of the tracts. Harper fault disconformably overlie thick bedded undifferentiated carbon- ates and quartzite of the Pinguicula views of the edifice in which paleo- The upper suite consists of Group or Wernecke Supergroup, slopes and tapering flows dip away three members: D (rhyolite), E attesting to uplift and erosion of the from the volcanic edifice. Other steep (andesite), and F (andesite). The rela- fault block prior to volcanism. exposures reveal that the edifice was tive timing of eruption and original Volcanic members A and B form an unevenly dissected during, or shortly distribution of these distinct units edifice up to 1200 m thick. Some of after, members A and B were extruded, remain unclear. In different localities, the later eruptions were subaerial, pro- resulting in overlaps by tuff-breccia, each unit unconformably overlies ducing agglutinated spatter cones and lapilli tuff, and block-and-ash breccia members A–C. Rhyolite of member D hematitic, autobrecciated massive flows deposits of member C. The clasts are forms thick flows and probable domes, (Mustard and Roots 1997). Holocene either primary basaltic or derived from and was dated at 717.43 ± 0.14 Ma erosion has provided cross-sectional erosion (Mustard and Roots 1997). (U/Pb CA-ID-TIMS zircon; Macdon- 90 ald et al. 2010b). The age of the lower tions of the Fifteenmile Group (yellow in the Coal Creek inlier were con- members of the MHVC are unknown faults, Fig. 3). These structures have founded by large lateral facies change so the temporal and spatial relationship the same orientation as the Ogilvie in the Fifteenmile Group, in particular between the eruption of the lower and breccias (Thompson et al. 1987, 1994) within the Reefal assemblage. Conse- upper suites remains unconstrained and one of the two major mafic dyke quently, these earlier maps include (Mustard and Roots 1997). Member E sets, suggesting either a genetic rela- many inferred thrust faults (Thompson forms cliff exposures of columnar- tionship or reactivation of earlier et al. 1994), which we have reinterpret- jointed and shattered massive flows; structures that generated the Ogilvie ed as predominantly conformable con- these prograde over an apron of angu- breccias. It is also unclear if the fault- tacts along abrupt lithological changes. lar flow shards (‘hydroclastic breccia’) ing in the lower stratigraphy of the Fif- that extend over an older edifice. teenmile Group represents a continu- CHEMOSTRATIGRAPHY Member F andesites form pillowed um of activity or the reactivation of Methods flows, breccias, tuffs, and invasive older syn-Pinguicula structures. These We report 1386 new carbonate carbon flows that interfinger with and intrude faults control the sedimentation pat- and oxygen isotope measurements (see into diamictites of the Rapitan Group, terns and stratal geometries between, data repository). Samples were cut which includes a ~1-m thick, green to and within, the Pinguicula Group and perpendicular to lamination, revealing pink, brecciated tuff that was dated at lower units of the Fifteenmile Group, internal textures and between 5 and 20 716.47 ± 0.24 Ma (U/Pb CA-ID-TIMS forming two separate WSW–ENE ori- mg of powder were micro-drilled from zircon; Macdonald et al. 2010b). ented troughs (Figs. 3, 6 and 7). The the individual laminations (where visi- Pinguicula Group stratigraphy appears ble), avoiding veining, fractures, and Mafic Dykes to thicken to the southwest into the siliciclastic components. Subsequent 13 18 Two sets of mafic dykes are present in bounding WSW–ENE faults and these δ Ccarb and δ Ocarb analyses were per- the Coal Creek inlier. One set is ori- strata do not appear farther to the formed on aliquots of this powder, ented WSW–ENE and predominantly south. The faults are truncated and acquired simultaneously on a VG Opti- intrudes the Wernecke Supergroup capped by the lowermost sequence of ma dual inlet mass spectrometer (Fig. 3). These dykes are likely correla- the Reefal assemblage of the Fifteen- attached to a VG Isocarb preparation tive with the sheared mafic rocks that mile Group, but the fault-generated device (Micromass, Milford, MA), in are in fault contact with the Fifteen- topography was preserved through the Harvard University Laboratory for mile Group near Mt. Gibben in section deposition of the remaining Reefal Geochemical Oceanography. Micro- E1002 (Fig. 3) and multiple intrusions assemblage and is highlighted by the drilled samples were reacted in a com- associated with the WSW–ENE orient- distribution of stromatolite reef devel- mon, purified H3PO4 bath at 90°C ed Ogilvie breccias. In section E1003 opment. where evolved CO2 was collected cryo- (Fig. 3), an ESE–WNW oriented dyke A second set of WNW–ESE genically and analyzed using an in- also intrudes Pinguicula A. oriented, NNE-side down normal house reference gas. External error A second set of dykes is ori- faults cuts the entire Fifteenmile (1σ) from standards was better than ± ented NNW–SSE and intrudes strata Group and underlying strata (Fig. 3). 0.1‰ for both δ13C and δ18O. Samples up through the lower MHVC. These These faults were active during deposi- were calibrated to VPDB (Vienna Pee- dykes are associated with chaotic tion of the Mount Harper Group and Dee Belemnite) using the Carrara Mar- deformation in the Lower Mount are subparallel to the dykes that ble standard. Increasing the reaction Harper Group, indicating that these intrude all of the Fifteenmile and times (~7 minutes) minimizes any rocks were still soft sediments when Mount Harper Group stratigraphy. potential memory effect resulting from the second suite was emplaced. No Syn-extensional emplacement of the the common acid-bath system, which dykes have been observed to intrude dykes is further demonstrated by soft- is included in the precision estimates the Rapitan Group. Thus, the sediment deformation around many of noted above. Carbon (δ13C) and oxy- NNW–SSE dykes appear to be associ- the intrusions in the fault-controlled gen (δ18O) isotopic results are reported ated with the ca. 717 Ma upper MHVC Lower Mount Harper Group. A third in per mil notation of 13C/12C and and predate the ca. 716 Ma Rapitan set of normal faults, oriented ~E–W, 18O/16O, respectively, relative to the Group. cut the overlying Windermere Super- standard VPDB. group and, in places, were reactivated STRUCTURE as structures that offset the Cambri- Results Our geological mapping has revealed an–Devonian Bouvette Formation; the Carbon isotope chemostratigraphy of two distinct sets of Precambrian struc- age and tectonic significance of these the Fifteenmile Group was performed tures within the Coal Creek inlier (Fig. faults are unclear. to test local, regional, and global corre- 3). The oldest structures, predomi- Cordilleran (Cretaceous) N- lations through large facies changes. nantly NNW-side down normal faults and NW-vergent thrust faults are com- In the basal Gibben formation of the oriented ~070°, cut the Chandindu mon south of the Dawson Thrust and Fifteenmile Group, δ13C values rise formation and all of the underlying on the western margin of the Coal from ~0 to +4‰, and is a consistent stratigraphy and were active during Creek inlier, but largely absent within trend throughout the inlier (Figs. 5 and deposition of the Pinguicula Group the core of the inlier. Early attempts at 6). Carbon isotope values in thin car- and the Chandindu and Gibben forma- mapping the Proterozoic stratigraphy bonate interbeds, within siliciclastic- GEOSCIENCE CANADA Volume 39 2012 91 dominated strata of the overlying DISCUSSION lain by the Pleasant Creek Volcanics, Chandindu formation and lower por- Regional Correlations which may be correlative with the ca. tion of the Reefal assemblage, are Tatonduk Inlier 717 Ma Mount Harper Volcanic Com- highly variable. This is likely due, in Young (1982) broadly divided Protero- plex (Macdonald et al. 2011). Glacial part, to local re-mineralization of zoic strata discontinuously exposed in diamictite with iron formation (Young organic matter and proportionately the Tatonduk inlier, a faulted anticline 1982) is correlative with the Rapitan greater contribution of 13C-depleted near the Yukon–Alaska border (~85 Group in the Coal Creek inlier and the authigenic cements to the whole-rock km NW of Mount Harper), into the Mackenzie Mountains (Macdonald et al carbonate content. Nonetheless, more upper and lower Tindir Group. The 2010b; Macdonald and Cohen 2011). carbonate-rich facies at the top of stratigraphically lowest exposed out- Numerous mafic dykes intrude the sequence 4b in the Mount Harper crop consists of ~150 m of grey to pre-Rapitan Group strata, including the composite section (Fig. 5), show con- dark brown shale, siltstone and sand- exposures at Mt. Slipper, whereas the sistent values around 0‰ that rise stone (‘mudstone’ unit of Young, Rapitan Group and overlying stratigra- steadily up-section to very heavy values 1982). These strata are succeeded by phy do not host these intrusions (Mac- (~+4‰). ~100 m of thin-bedded orange to light donald et al. 2010a). The stromatolite reefs of blue dolomicrite, followed by ~275 m sequence 5 of the Reefal assemblage of shallow-water dolostone dominated Hart River Inlier have δ13C values that average ~+4‰. by stromatolitic buildups that are cor- Abbott (1997) defined six Pinguicula- However, lateral gradients are present relative with either Pinguicula B/C or correlative units beneath the Callison in coeval strata. Above the basal the Gibben formation (Macdonald et Lake dolostone in the Hart River inlier. flooding surface of sequence 6, δ13C al. 2011). The carbonates are overlain The Pinguicula units include: A, B and values increase further to ~+8‰. This by black shale and an additional 500 m C, and three discontinuous members sequence contains the 811.5 ± 0.1 Ma or more of poorly exposed interbed- of unit D. Unit PD1 consists of a ash bed (Macdonald et al. 2010b). ded sandstone and shale. series of shale to sandstone cycles that Above the ash bed, ´13C values At Mt. Slipper, near the north- broadly make up a single depositional decrease smoothly to values as low as - ernmost exposures in the Tatonduk sequence. Unit PD1 is conformably 6‰ (Figs. 5 and 6). However, the full inlier, carbonate strata previously overlain by a carbonate sequence ~14‰ isotope excursion is not present mapped as the Cambrian–Ordovician capped by a thick, shoaling-upward, in some sections because the interval is Jones Ridge Limestone (Norris 1982; medium-bedded, bluish-grey dolostone shale-dominated (e.g., in the Mount Young 1982; Morrow 1999), were rein- with abundant ooids and microbialami- Harper composite section, Fig. 5). In terpreted based upon new mapping nite (PD2), which is, in turn, succeeded other sections, the excursion is cut out and carbon and strontium by mud-cracked siltstone and shale of by erosional surfaces (e.g., in the Mt. chemostratigraphy to be part of the PD3 (Halverson et al. 2012). The basal Gibben composite section, Fig. 5). Fifteenmile Group (Macdonald et al., siltstone–sandstone sequence of PD1 The most complete section of the 2010a, b, 2011). The exposures of the is regarded as the basal sequence of excursion is exposed at Reefer Camp Fifteenmile Group at Mount Slipper the Fifteenmile Group (S1), which is (section G021), which was measured consist of >350 m of predominantly equivalent to the thin sandstone unit at from a paleo-high developed above a stromatolitic dolostone and an addi- the base of the Gibben formation in reef core (Fig. 6). There, the S7a tional ~500 m of black shale with the Coal Creek inlier. Unit PD2 is transgression is carbonate dominated, interbedded quartz sandstone and equivalent to the carbonates of the so the whole excursion is preserved minor carbonate that are assigned to Gibben formation in the Coal Creek along with two additional smaller the Reefal assemblage. Scale microfos- inlier. Unit PD3 is composed of excursions in the S7a highstand and sils were located within the top 10 m brown sandstone with minor orange S7c (Fig. 6). Although a weak covari- of the Reefal assemblage at Mt. Slipper dolostone, which we correlate with the ance between δ13C and δ18O can be (Macdonald et al. 2010a; Cohen et al. Chandindu formation (Halverson et al. observed through these excursions (see 2011; Cohen and Knoll, 2012). These 2012). Correlation between the Coal data repository), lateral reproducibility strata are succeeded by a yellow-weath- Creek and Hart River inliers indicates through different facies precludes ering dolostone with common intra- that all of the upper Fifteenmile large-scale diagenetic alteration. clast breccia, black chert nodules, and Group is missing in the Hart River inli- In the Craggy dolostone, δ13C green siltstone and shale interbeds that er at the angular unconformity beneath values increase steadily up-section and are assigned to the Craggy dolostone. the Callison Lake dolostone (Abbott plateau at ~4‰. Although these The remaining stratigraphy on Mt. 1997; Macdonald and Roots 2010). dolomites are dominated by cement Slipper and the youngest exposed stra- and full of exposure surfaces, the δ13C ta in this part of the inlier consists of Wernecke and Mackenzie Moun- trends are consistent along strike and heavily silicified dolostone, and it is tains show no covariance with oxygen iso- unclear if this dolostone is temporally Recent stratigraphic studies in the Wer- topes (see data repository). equivalent to the Craggy dolostone or necke Mountains (Thorkelson et al. Callison Lake dolostone. 2005; Medig et al. 2010; Turner 2011) In the southern part of the have assigned various portions of units inlier, the Fifteenmile Group is over- D–F of the Pinguicula Group of Eis- 92

Figure 9. Correlation of sequences between the Fifteenmile Group, Little Dal Group, and Shaler Supergroup as indicated by carbon isotope chemostratigraphy. Schematic stratigraphy and symbology follows Figure 2. Red squares are from stratigraphic sections located near Mt. Gibben, green squares are from sections located near Reefer camp, and blue dots are from sections near Mount Harper (see Figure 3). Particular sections are noted with coloured bars and detailed in Figures 5 and 6. Carbon isotope data from the Mackenzie Mountains is after Halverson (2006) and data from Victoria Island is after Jones et al. (2010). Refer to Figure 2 for abbreviations of formations. bacher (1981) to the Hematite Creek, inlier, and that the Tarn Lake Forma- the Little Dal Group. These correla- Katherine, and Little Dal groups. tion and Katherine Group are equiva- tions suggest that the Gypsum forma- Moreover, Turner (2011) formally lent to PD3 in the Hart River inlier tion and the Rusty Shale formation divided the Hematite Creek Group and the Chandindu formation in the were deposited during the S6 LST (Fig. into the Dolores Creek, Black Canyon Coal Creek inlier (Figs 2 and 9). 9). Negative δ13C values within a trans- Creek, and Tarn Lake formations. This Halverson (2006) presented gressive sequence tract in the middle work facilitates correlation of the Coal ´13C data for the Little Dal Group in Upper Carbonate formation (Halver- Creek strata with particular formations the Mackenzie Mountains that we can son 2006) can be correlated with the in the Mackenzie Mountains and Shaler use to test proposed lithostratigraphic negative values in S7 of the Fifteen- supergoups. Extension of our pro- correlations (Fig. 9). In regards to this mile Group (Fig. 9). Exact correlations posed correlation scheme for the Pin- chemostratigraphic correlation, the between the upper portion of the guicula and Fifteenmile groups in the Reefal assemblage displays a rise in Upper Carbonate formation and the Tatonduk, Coal Creek and Hart River δ13C from 0 to +5‰ that mirrors the Craggy dolostone remain unclear. inliers to the Wernecke Mountains sug- δ13C profile of the Platform Assem- gests that the Dolores Creek Forma- blage of the Little Dal Group. Victoria Island tion is equivalent to unit PD1 in the Extremely positive δ13C values A composite carbon isotope curve Hart River inlier, that the Black (>+8‰) at the base of sequence 6 in through the upper Shaler Supergroup Canyon Creek Formation is equivalent the Fifteenmile Group are correlative was recently published by Jones et al. to PD2 in the Hart River inlier and the with similar values in the lower portion (2010), who suggested that the Aok Gibben formation in the Coal Creek of the Upper Carbonate formation of Formation could be correlative with GEOSCIENCE CANADA Volume 39 2012 93 the basal Little Dal Group. Here we 2010), which is based on the Platfor- served. Thus, if authigenesis is follow previous lithostratigraphic cor- mal Assemblage of the Little Dal responsible, it must have been wide- relation schemes (e.g. Rainbird et al. Group, may be exaggerated. More- spread but episodic in the basin. 1996), which correlate unit K6 of the over, isotopically heavy intervals in the Katherine Group with the Aok Forma- Gibben formation (Figs. 6 and 10) Basin Formation in the Coal Creek tion and, in turn, the Chandindu for- indicate that this rise was not steady Inlier mation; however, these correlations are and that there is probably significant Basin Event 1: The Pinguicula prel- limited by the lack of data in unit K6 variability in late Mesoproterozoic and ude of the Katherine Group. Sequence S4 early Neoproterozoic carbon isotope Active tectonism during deposition of of the Reefal assemblage is broadly records that remains to be fully eluci- the Pinguicula Group is demonstrated correlative with the Platform Assem- dated. by: 1) olistostromes of the Gillespie blage in the Mackenzie Mountains and Macdonald et al. (2010) sug- Lake Group within Pinguicula Group Boot Inlet Formation on Victoria gested that the 811.5 ± 0.1 Ma ash bed strata that increase in abundance Island. Sequence S5 can be correlated dates the onset of the Bitter Springs towards the south; 2) lateral facies with the Grainstone formation and the isotopic stage. This interpretation is changes in Pinguicula B/C with stro- Fort Collinson and Jago formations on further supported by additional high- matolitic reefs built on paleo-highs that Victoria Island. Like the Gypsum For- resolution chemostratigraphic sections grade to the SSE into laminated mation, evaporites of the Minto Inlet through carbonate-rich strata of the dolomicrite; 3) lateral thickness varia- Formation appear to record a period upper Reefal assemblage; however, this tions in all of the units of the Pinguic- of lowstand represented by prograda- work has revealed three carbon iso- ula Group. These thickness variations tion of giant reef complexes in the topic excursions that do not have obvi- do not merely represent erosion associ- LST of S3B. Extremely positive δ13C ous counterparts elsewhere (Fig. 6). ated with the sub-Gibben unconformi- values (>+8‰) in the lower portion of The Bitter Springs anomaly in Svalbard ty, but instead record internal thinning the Wynniatt Formation can be corre- and Australia has a double peak, with and truncation due to depositional lated with those at the base of S6 in slightly positive values between the onlap of topographic relief. the Fifteenmile Group (Fig. 9). We major negative excursions (Halverson The extent to which the over- follow Jones et al. (2010) and correlate et al. 2007; Swanson-Hysell et al. lying Fifteenmile Group follows the the δ13C downturn in the middle Wyn- 2010). In this correlation scheme, the syn-tectonic depositional patterns of niatt transgression with the Bitter first downturn in the TST of S7a of the Pinguicula Group in the Coal Springs isotopic stage. These correla- the Reefal assemblage, which begins at Creek inlier is remarkable. This could tions (Fig. 9) suggest that rich micro- ca. 811.5 Ma, is equivalent to the G1 be interpreted in one of two ways: 1) fossil assemblages in the lower Wynni- surface in Svalbard, and the return to the Pinguicula Group is an older basin att Formation (Butterfield and Rainbird positive values in the HST of S7C at and the Fifteenmile Group extension 1998; Butterfield, 2005a, b) and less the top of the Reefal assemblage is and depositional patterns followed pre- diverse assemblages in the Rusty Shale equivalent to the S1 surface. existing crustal weaknesses; 2) the Pin- (Butterfield and Rainbird, 1998) are Another interesting feature of guicula Group was deposited in half stratigraphically below scale microfos- the δ13C curve from the Fifteenmile graben along NNW-side down normal sils from the Fifteenmile Group Group is that the major negative faults and represents an early phase of (Cohen et al. 2011; Cohen and Knoll, downturn at the base of the Reefal early Neoproterozoic extension that 2012). assemblage corresponds with the maxi- culminated in the deposition of the mum flooding surface of sequence S7. Fifteenmile Group. Implications for Neoproterozoic This can be interpreted in at least three Carbon Isotope Chemostratigraphy ways: 1) there was a global decrease in Basin Event 2: Lower Fifteenmile Halverson et al. (2006) suggested that the percent of carbon buried as organ- extension the rise in δ13C values from 0‰ to ic carbon; 2) the transgression was The lowermost Fifteenmile Group is +5‰ in the Platformal Assemblage of eustatic and corresponded to the addi- highly variable in thickness with depo- the Little Dal Group represents a glob- tion and remineralization of isotopical- sitional patterns defined by small fault- al rise from a carbon cycle that aver- ly light carbon to the ocean/atmos- bounded sub-basins, resulting in aged 0‰ in the Mesoproterozoic to phere, which drove both a negative wedge-shaped stratal geometries and one that averaged +5‰ in the Neo- carbon isotope excursion, warming, inferred onlapping patterns (Figs. 5 proterozoic. With no direct age con- and transgression; or 3) isotopically and 6). Northeast of Mount Harper, straints on the base of these isotopic light authigenic carbonate was prefer- these faults cut through the Gibben profiles, the thickness of the strata up entially formed locally during trans- and Chandindu formations as NNW- to the ~811 Ma ash bed is dependent gressive sequences. The data presented side down normal faults (Fig. 3) that on accumulation rates. It is likely that here demonstrates that not all of the are capped by the overlying Reefal platformal and stromatolite dominated transgressive sequences in the succes- assemblage. facies have higher sedimentation rates sion host negative isotope excursions, The interpretation of the than basinal facies, and consequently and that the negative δ13C excursion at geometry of these structures depends the duration of the early Neoprotero- the base of S7 is broadly reproducible on the degree to which the Yukon zoic +5‰ plateau (Halverson et al. in the basin where the sequence is pre- block has been affected by post-811 94

Ma vertical axis tectonic rotations. A Creek inlier and this unconformity both the formation and the breakup of large Neoproterozoic counterclockwise places the Callison Lake dolostone on Rodinia has remained elusive. Situated (CCW) rotation and dextral displace- the lower Fifteenmile Group in the at the NW corner of Laurentia, and in ment between the Yukon block and Hart River inlier (Abbott 1997; Mac- the centre of Rodinia (Li et al. 2008b), Laurentia was first proposed by Eis- donald and Roots 2010; Halverson et the Yukon occupies an important posi- bacher (1981) and developed further al. 2012). Silicification typically tion for distinguishing between tecton- by Aitken and McMechan (1991) and extends 100s of metres below this ic events occurring on the northern Abbott (1996) who incorporated paleo- unconformity surface, which also dis- and western margins of Laurentia. magnetic evidence (Park and Jefferson plays evidence of localized paleokarsti- Recent paleomagnetic studies provide a 1991; Park et al. 1992). The dextral fication (Mustard and Donaldson, Rodinia reconstruction that is “longer- displacement hypothesis originated as a 1990). Depositional patterns of the lasting and tighter-fitting” (Li and response to abrupt facies changes in Callison Lake dolostone and the Evans 2011), and these data require the MMSG across the Snake River Mount Harper Group are completely that Australia and Laurentia came Fault (Fig. 1) and paleocurrent direc- divorced from those of the underlying together after 1070 Ma with a ‘missing tions in the Wernecke Supergroup Fifteenmile Group suggesting the com- link’ presiding in-between, and subse- (Eisbacher 1981; Aitken and mencement of an additional basin- quently separated between ca. 750 and McMechan 1991). Right-lateral dis- forming episode. Locally, the lower 650 Ma. Paleomagnetic and placement occurred in the late Neo- Mount Harper Group paracon- geochronologic data indicate that proterozoic along the Richardson Fault formably overlies shale in the upper- South China may be the ‘missing link’ Array (Fig. 1) and these faults were most Callison Lake dolostone and (Li et al., 1995, 2008b). South China is reactivated during the Cretaceous unconformably overlies the Quartet a composite Neoproterozoic continent (Norris 1997). A post-Cryogenian Group (Fig. 3), which suggests pro- consisting of the Cathaysia and CCW rotation was further suggested nounced synsedimentary fault activity Yangtze blocks, which converged dur- by paleomagnetic studies on the Mount (Mustard, 1991). Clasts within the ing the ca. 835 Ma Sibao orogeny Harper Volcanic Complex (Park et al. conglomerate display an inverted (Wang et al. 2012). In the ‘missing 1992). Park et al. (1992) proposed an stratigraphy, with clasts of the link’ model, the Cathaysia Block was a 80° CCW rotation, however, he used youngest units on the footwall domi- fragment of Mesoproterozoic Lauren- earlier dates with large error on the nating the lowest conglomerates on the tia and the Yangtze Block provided Mount Harper Volcanic Complex and hanging-wall, and clasts of older units westerly-derived 1600–1490 Ma zircons correlated the virtual pole with that of becoming more common upwards in to the Belt Supergroup (Ross et al. the Little Dal Basalt. The new ages on the congolomerate, demonstrating that 1992; Ross and Villeneuve 2003). The the Mt. Harper Volcanic Complex and it formed while progressively eroding Sibao Orogeny may have also provided the Franklin LIP (Macdonald et al. strata on the footwall. Much of the a more local source of Grenville-age 2010) suggest this pole should be cor- overlying Mount Harper Volcanic 1.2–1.0 Ma zircons to the western mar- related with the grand mean pole on Complex formed via subaerial erup- gin of Laurentia (Li et al. 2008a) that the Franklin LIP (Denyszyn et al. tions, suggesting that the volcanics have previously been attributed to a 2009) to refine this rotation. This filled much of the graben (Fig. 9). transcontinental river system (Rainbird would reduce the rotation to 66° CCW. Where the volcanics taper to the north, et al. 1997). However, no early Neo- If the paleomagnetic pole on the the overlying glacial diamictite of the proterozoic foreland basin or orogen Mount Harper Volcanic Complex (Park Rapitan Group thickens significantly. has been identified on the western et al. 1992) stands further scrutiny, The Callison Lake dolostone margin of Laurentia to suggest a link then the pre-811 Ma WSW–ENE and Mount Harper Group occupy an to this orogenic event. Possible excep- structures in the Coal Creek inlier equivalent stratigraphic position with tions occur in the Coppermine homo- would rotate roughly parallel with the the Coates Lake Group of the cline (Fig. 1), where two sets of struc- strike of the Mackenzie Arc and the Mackenzie Mountains (Macdonald and tures deform the ca. 1270 Ma Copper- Fifteenmile Group would represent the Roots, 2010). In the Mackenzie Moun- mine River Group and predate the conjugate margin of a graben formed tains, the Coates Lake Group and Little Shaler Supergroup (Hildebrand and opposite of the MMSG. If the paleo- Dal Basalt unconformably overlie the Baragar 1991), and in the Wernecke magnetic pole cannot be reproduced MMSG in NNW-oriented grabens that Mountains, where NW-vergent folds in and the Yukon block has not moved formed in response to right-lateral the Hematite Creek and Katherine substantially relative to the autochthon, transtension (Jefferson 1978). Coates groups have been assigned to the Corn then the WSW–ENE structures would Lake- to Rapitan-age folding is also Creek Orogeny (Eisbacher 1981; represent extension on the NW margin present in the Mackenzie Mountains Thorkelson 2000; Thorkelson et al. of Laurentia. and is responsible for paleohighs that 2005). Neoproterozoic folding has formed along transpressional segments also been described in the Coates Lake Basin Event 3: Mount Harper exten- of transfer zones (Jefferson 1978). and Rapitan groups in the Mackenzie sion Mountains (Helmstaedt et al.1979; Eis- As discussed above, the Craggy dolo- The Make-Up and Break-Up of bacher 1981), and in the Shaler Super- stone is unconformably overlain by the Rodinia group on Victoria Island (Heaman et Callison Lake dolostone in the Coal The exact timing and geometry for al. 1992; Bedard et al. 2012), but these GEOSCIENCE CANADA Volume 39 2012 95 structures appear to be too young to 810 (Wingate et al. 1998; Li et al. 1999; basin formation on the western margin be correlative with the Sibao orogeny. Wang et al., 2008) suggests a mechanis- of Laurentia remains enigmatic. As The Fifteenmile Group and tic link. We propose that these strata discussed above, the presence of both equivalent strata in the Mackenzie were accommodated by extension and Cryogenian normal faults and folding Mountains and Victoria Island, can be the subsequent thermal decay associat- implies a transtensional–transpressional broadly correlated to the Shihuiding ed with the passing of Rodinia over a setting for Windermere-age rifting (Jef- Formation of the Cathaysia Block, and plume. In this model, the Reefal ferson and Parrish 1989). Transtension the Ziajiang, Danzhou and Banxi assemblage and Craggy dolostone are may further account for the irregular groups of the Yangtzee Block (Wang associated with the thermal decay of distribution of Cryogenian strata in et al. 2011), the lower Callana Group in this plume. Deposition culminated Yukon (Macdonald et al. 2011) and the South Australia, the Bitter Springs For- with the intrusion of the 780 Ma Gun- lack of significant crustal thinning until mation and equivalents in central Aus- barrel dykes—the nature of this the latest Ediacaran (Colpron et al. tralia (Walter et al. 1995). Like the Fif- igneous event remains poorly under- 2002), consistent with thermal subsi- teenmile Group, these Chinese basins stood. This model is further consis- dence models that indicate final rifting also contain ca. 810 Ma tuff horizons tent with the inference of Rainbird et in the earliest Cambrian (Bond and (Wang et al. 2012). The ‘missing link’ al. (1996) that Sequence B formed in Kominz 1984). Full description of model predicts that more ca. 800 Ma an intracratonic basin. Cryogenian and Ediacaran basins is grains from the Sibao orogeny will be The ca. 717 Ma NNE-side beyond the scope of this paper and the discovered in the uppermost Fifteen- down normal faults in the Coal Creek later Neoproterozoic tectonic evolu- mile Group or overlying strata. Inter- inlier represent a reactivation of the tion of NW Laurentia remains to be estingly, significant ca. 800 Ma popula- NW margin of Laurentia. Geological elucidated with future work. tions have been discovered in the and geochronological data suggest that Uinta Mountains Group of Utah Siberia occupied a position north of CONCLUSIONS (Dehler et al. 2010), which may have the Yukon during the Neoproterozoic Geological mapping, chemostratigra- been sourced from South China. (Rainbird et al. 1998). Moreover, dykes phy and sequence stratigraphic analysis Additionally, new age constraints on of approximately Franklin age are of Neoproterozoic strata in Yukon successions in the western US indicate present in southwestern Siberia (Glad- motivate revised correlation of the that there are no known basins that kochub et al. 2006; Bedard et al. 2012;). early Neoproterozoic deposits of formed between 1.0 and 0.8 Ga Rainbird (1993) further documented northwest Canada. These results between 62° N and Mexico (Dehler et fault-bounded graben with coarse ter- demonstrate that at least three and al., 2010, 2011), such that the basin restrial fill in the upper Shaler Super- possibly four basin-forming events are forming event that accommodated the group, immediately beneath the ca. 723 recorded in Neoproterozoic strata of Fifteenmile Group and equivalents in Ma Natkusiak basalts. Although a Yukon. The Pinguicula Group consti- the Shaler Supergroup and MMSG is a record of later Cryogenian thermal tutes the oldest succession and its age phenomenon of the NW margin of subsidence is not present in Victoria and accommodation history remain Laurentia and cannot represent rifting Island where there is no section pres- poorly constrained. Subsidence and on the whole of the western margin, ent above the Natkusiak basalts (Rain- deposition of the Fifteenmile Group contrary to the simple-shear rift model bird 1993), a Cryogenian passive mar- initiated prior to ~811 Ma as a result proposed to accommodate the MMSG gin succession on the northern margin of NNW-side down normal faulting (Turner and Long 2008). We suggest of Laurentia may be recorded in the (present coordinates). The extension instead that the inferred NE–SW ori- subsurface west of Melville Island that accommodated the Fifteenmile ented faults in the MMSG of Turner (Helwig et al. 2011) and in the Katak- Group is coincident with the passing and Long (2008) are coeval with the turuk Dolomite on the parautochtho- of a plume under Rodinia and the faults in the basal Fifteenmile Group nous North Slope subterrane (Mac- emplacement of large igneous and also represent normal faults rather donald et al. 2009). Thus, a scenario provinces and the formation of failed than transfer faults. This is consistent consistent with all of these data is that intracontinental rift basins in South with Aitken’s (1981) previous interpre- extension occurred in the early Neo- China and Australia. Large stromato- tation of the Little Dal Group, which proterozoic between Siberia and north- lite-cored reef systems of the Reefal suggested deepening to the NNW. west Laurentia, creating space between assemblage developed on these paleo- Based on the assumption that the two cratons and separating their highs and prograded to the NNW in a the early Neoproterozoic conjugate respective APW paths (Rainbird et al. series of highstand systems tracts, margin to Laurentia was South China, 1998; Khudoley et al. 2001; Evans shedding reworked carbonate into and we propose a new model for the early 2009); however this extension may not gradually filling deep-water, shale sub- Neoproterozoic tectonic evolution of have manifested itself in full rifting basins. The basin was reactivated with northwest Canada. The coincidence with the development of oceanic crust, ca. 717 Ma NNE-side down normal between basin formation in South such that both margins were later faulting in the Yukon and the emplace- China, Australia, and NW Canada at affected by additional extension and ment of the Franklin large igneous ca. 830 Ma, and the emplacement of the emplacement of the ca. 720 Ma province on the northern margin of the Gubei and Gairdner LIPs in South Franklin LIP. Laurentia. China and Australia between 830 and The nature of Cryogenian 96

ACKNOWLEDGMENTS curves for the early Paleozoic miogeo- E. K., Karlstrom, K. E., Williams, M. We thank Paul Hoffman for inspiration cline, southern Canadian Rocky L., Jercinovic, M. J., Gehrels, G., and his stamina for discussing geology Mountains: implications for subsi- Pecha, M., and Heizler, M. T., 2011, late into the night. The Yukon Geolog- dence mechanisms, age of breakup, ChUMP Connection (Chuar-Uinta ical Survey (FM and GH), NSERC and crustal thinning: Geological Socie- Mountain-Pahrump): Geochronologic ty of America Bulletin, v. 95, no. 2, p. constraints for correlating ca. 750 Ma (GH), the MIT node of the NASA 155-173. Neoproterozoic successions of south- Astrobiology Institute (FM), and the Butterfield, N. J., 2005a, Probable Protero- western Laurentia, in Proceedings American Chemical Society Petroleum zoic fungi: Paleobiology, v. 31, no. 1, Geologiacl Society of America Research Fund (GH) have supported p. 165-182. Abstracts with Programs, Denver, this project. We thank Fireweed Heli- -, 2005b, Reconstructing a complex early 2011, Volume 43, p. 55. copters for reliable transportation, and Neoproterozoic eukaryote, Wynniatt Dehler, C. M., Fanning, C. M., Link, P. K., Maurice Colpron and Don Murphy for Formation, Arctic Canada: Lethaia, v. Kingsbury, E. M., and Rybczynski, D., helpful conversations. We thank Dan 38, no. 2, p. 155-169. 2010, Maximum depositional age and Schrag, Sasha Breus, and Greg Eis- Butterfield, N. J., and Rainbird, R. H., provenance of the Uinta Mountain chied for assistance in the Laboratory 1998, Diverse organic-walled fossils, Group and Big Cottonwood Forma- including “possible dinoflagellates,” tion, northern Utah: Paleogeography for Geochemical Oceanography at from the early Neoproterozoic of of rifting western Laurentia: Geologi- Harvard University. We would also like Arctic Canada: Geology, v. 26, no. 11, cal Society of America Bulletin, v. 122, to thank the Roots family for their p. 963-966. no. 9/10, p. 1686-1699. hospitality and generosity. Cecile, M. P., 1982, The lower Paleozoic Delaney, G. D., 1981, The mid-Proterozoic Misty Creek Embayment, Selwyn Wernecke Supergroup, Wernecke REFERENCES Basin, Yukon and Northwest Territo- Mountains, Yukon Territory, in Camp- Abbott, G., 1996, Implications of probable ries: Geological Survey of Canada bell, F. H. A., ed., Proterozoic basins late Proteorozoic dextral strike-slip Bulletin, v. 335, p. 78. of Canada: Ottawa, Geological Survey movement on the Snake River fault, in Cecile, M.P., 2000, Geology of the north- of Canada Paper 81-10, p. 1-23. Proceedings Slave-Northern Cordillera eastern Niddery Lake map area, east Denyszyn, S. W., Davis, D. W., and Halls, Lithosphere Experiment, Lithoprobe central Yukon and adjacent Northwest H. C., 2009, Paleomagnetism and U- Report #50. Territories: Geological Survey of Pb geochronology of the Clarence Abbott, G., 1997, Geology of the Upper Canada Bulletin, v. 553, p. 120. Head dykes, Arctic Canada: orthogo- Hart River Area, Eastern Ogilvie Cecile, M. P., Marrow, D. W., and Williams, nal emplacement of mafic dykes in a Mountains, Yukon Territory G. K., 1997, Early Paleozoic (Cambri- large igneous province: Canadian Jour- (116A/10, 116A/11): Exploration and an to Early Devonian) tectonic frame- nal of Earth Sciences, v. 46, p. 155- Geological Services Division, Yukon work, Canadian Cordillera: Bulletin of 167. Region, Bulletin 9, p. 1-76. Canadian Petroleum Geology, v. 45, p. Donnadieu, Y., Godderis, Y., Ramstein, G., Aitken, J. D., 1981, Stratigraphy and Sedi- 54-74. Nedelec, A., and Meert, J., 2004, A mentology of the Upper Proterozoic Cohen, P. A., and Knoll, A. H., 2012, Scale ‘snowball Earth’ climate triggered by Little Dal Group, Mackenzie Moun- microfossils from the mid-Neopro- continental break-up through changes tains, Northwest Territories, in Camp- terozoic Fifteenmile Group, Yukon in runoff: Nature, v. 428, p. 303-306. bell, F. H. A., ed., Proterozoic Basins Territory: Journal of Paleontology, v. Dudás, F. O., and Lustwerk, R. L., 1997, of Canada, Geological Survey of 86, no. 5, p. 775-800. Geochemistry of the Little Dal Canada Paper 81-10, p. 47-71. Cohen, P. A., Schopf, J. W., Kudryaytsev, basalts: continental tholeites from the Aitken, J. D., and Long, D. G. F., 1978, A., Butterfield, N. J., and Macdonald, Mackenzie Mountains, Northwest Ter- Mackenzie tectonic arc—Reflection of F. A., 2011, Phosphate biomineraliza- ritories, Canada: Canadian Journal of early basin configuration?: Geology, v. tion in mid-Neoproterozoic protists: Earth Sciences, v. 34, p. 50-58. 6, p. 626-629. Geology, v. 39, no. 6, p. 539-542. Eisbacher, G. H., 1981, Sedimentary tec- Aitken, J. D., and McMechan, M. E., 1991, Colpron, M., Logan, J. M., and Mortensen, tonics and glacial record in the Win- Middle Proterozoic assemblages, J. K., 2002, U-Pb zircon age constraint dermere Supergroup, Mackenzie Chapter 5, in Gabrielse, H., and for late Neoproterozoic rifting and ini- Mountains, northwestern Canada: Yorath, C. J., eds., Geology of the tiation of the lower Paleozoic passive Geological Survey of Canada Paper Cordilleran Orogen in Canada, Vol- margin of western Laurentia: Canadi- 80-27, p. 1-40. ume 4, Geological Survey of Canada, an Journal of Earth Sciences, v. 39, p. Evans, D. A. D., 2009, The palaeomagneti- p. 97-124. 133-143. cally viable long-lived and all-inclusive Bedard, J. H., Naslund, H. R., Nabelek, P., Dalziel, I. W. D., 1991, Pacific margins of Rodinia supercontinent reconstruc- Winpenny, A., Hryciuk, M., Macdon- Laurentia and East Antarctica-Aus- tion, in Murphy, J. B., Keppie, J. D., ald, W., Hayes, B., Steigerwaldt, K., tralia as a conjugate rift pair: Evidence and Hynes, A., eds., Ancient Orogens Hadlari, T., Rainbird, R. H., Dewing, and implications for an Eocambrian and Modern Analogues, Volume 327: K., and Girard, E., 2012, Fault-medi- supercontinent: Geology, v. 19, p. 598- London, Geological Society of Lon- ated melt ascent in a Neoproterozoic 601. don Special Publication, p. 371-404. continental flood basalt province, the Dalziel, I. W. D., 1997, Neoproterozoic- Furlanetto, F., Thorkelson, D. J., Davis, W. Franklin sills, Victoria Island, Canada: Paleozoic geography and tectonics: J., Gibson, H. D., Rainbird, R. H., and Geological Society of America Bul- review, hypothesis, environmental Marshall, D. D., 2009, Preliminary letin, v. 124, no. 5/6, p. 723-736. speculation: Geological Society of results of detrital zircon geochronolo- Bond, G. C., and Kominz, M. A., 1984, America Bulletin, v. 109, p. 16-42. gy, Wernecke Supergroup, Yukon, in Construction of tectonic subsidence Dehler, C. M., Crossey, L. J., Fletcher, K. Weston, L. H., Blackburn, L. R., and GEOSCIENCE CANADA Volume 39 2012 97

Lewis, L. L., eds., Yukon Exploration 337-350. geosynclinal concepts: Transactions of and Geology 2008: Whitehorse, YT, Harlan, S. S., Heaman, L. M., LeChemi- the Royal Society of Canada, v. 56, p. Yukon Geological Survey, p. 125-135. nant, A. N., and Premo, W. R., 2003, 55-84. Gabrielse, H., 1972, Younger Precambrian Gunbarrel mafic magmatic event: a Jones, D. S., Maloof, A. C., Hurtgen, M. T., of the Canadian Cordillera: American key 780 Ma time marker for Rodinia Rainbird, R. H., and Schrag, D. P., Journal of Science, v. 272, p. 521-536. plate reconstructions: Geology, v. 31, 2010, Regional and global chemostrati- Gladkochub, D. P., Wingate, M. T. D., Pis- p. 1053-1056. graphic correlation of the early Neo- arevsky, S. A., Donskaya, T. V., Heaman, L. M., LeCheminant, A. N., and proterozoic Shaler Supergroup, Arctic Mazukabzov, A. M., Ponomarchuk, V. Rainbird, R. H., 1992, Nature and tim- Canda: Precambrian Research, v. 181, A., and Stanevich, A. M., 2006, Mafic ing of Franklin igneous events, Cana- p. 43-63. intrusions in southwestern Siberia and da: Implications for a Late Proterozoic Kerans, C., Ross, G. M., Donaldson, J. A., implications for a Neoproterozoic mantle plume and the break-up of and Geldsetzer, H. J., 1981, Tectonism connection with Laurentia: Precambri- Laurentia: Earth and Planetary Science and depositional history of the an Research, v. 147, p. 260-278. Letters, v. 109, p. 117-131. Helikian Hornby Bay and Dismal Godderis, Y., Donnadieu, Y., Nedelec, A., Helmstaedt, H., Eisbacher, G. H., and lakes groups, District of Mackenzie, in Dupre, B., Dessert, C., Grard, A., McGregor, J. A., 1979, Copper miner- Campbell, F. H. A., ed., Proterozoic Ramstein, G., and Francois, L. M., alization near an intra-Rapitan uncon- Basins, Volume Paper 81-10: Ottawa, 2003, The Sturtian ‘snowball’ glacia- formity, Nite copper prospect, Geological Survey of Canada, p. 157- tion: fire and ice: Earth and Planetary Mackenzie Mountains, Northwest Ter- 182. Science Letters, v. 6648, p. 1-12. ritories, Canada: Canadian Journal of Khudoley, A. K., Rainbird, R. H., Stern, R. Goodge, J. W., Vervoort, J. D., Fanning, C. Earth Sciences, v. 16, p. 50-59. A., Kropachev, A. P., Heaman, L. M., M., Brecke, D. M., Farmer, G. L., Helwig, J., Kumar, N., Emmet, P., and Zann, A. M., Podkovyrov, V. N., Belo- Williams, I. S., Myrow, P. M., and Dinkelman, M. G., 2011, Regional va, V. N., and Sukhorukov, V. I., 2001, DePaulo, D. J., 2008, A positive test of seismic interpretation of crustal Sedimentary evolution of the Riph- East Antarctica-Laurentia juxtaposi- framework, Canadian Arctic passive ean-Vendian basin of southeastern tion within the Rodinia superconti- margin, Beaufort Sea, with comments Siberia: Precambrian Research, v. 111, nent: Science, v. 321, p. 235-240. on petroleum potential, in Spencer, A. p. 129-163. Gordey, S. P., and Anderson, R. G., 1993, M., Embry, A. F., Gautier, D. L., Kirschvink, J. L., 1992, Late Proterozoic Evolution of the northern Cordillera Stoupakova, A. V., and Sorensen, K., low-latitude global glaciation: the miogeocline, Nahanni map area (105 eds., Arctic Petroleum Geology, Vol- snowball earth, in Schopf, J. W., and I) Yukon and Northwest Territories: ume 35: London, Geological Society, Klein, C., eds., The Proterozoic Bios- Geological Survey of Canada Memoir, p. 527-543. phere: Cambridge, Cambridge Univer- v. 428, p. 214. Hildebrand, R. S., and Baragar, W. R. A., sity Press, p. 51-52. Hall, K. W., and Cook, F. A., 1998, Geo- 1991, On folds and thrusts affecting Li, Z.-X., and Evans, D. A. D., 2011, Late physical transect of the Eagle Plains the Coppermine River Group, north- Neoproterozoic 40° intraplate rotation foldbelt and Richardson Mountains western Canadian Shield: Canadian within Australia allows for a tighter- anticlinorium, northwestern Canada: Journal of Earth Sciences, v. 28, p. fitting and longer lasting Rodinia: Geological Society of America Bul- 523-531. Geology, v. 39, no. 1, p. 39-42. letin, v. 110, no. 3, p. 311-325. Hoffman, P. F., 1991, Did the breakout of Li, Z.-X., Kinny, P. D., and Wang, J., 1999, Halverson, G. P., 2006, A Neoproterozoic Laurentia turn Gondwanaland inside- The breakup of Rodinia: did it start chronology, in Xiao, S., and Kaufman, out?: Science, v. 252, no. 5011, p. with a mantle plume beneath South A. J., eds., Neoproterozoic Geobiology 1409-1412. China?: Earth and Planetary Science and Paleobiology, Volume Topics in Hoffman, P. F., Kaufman, A. J., Halverson, Letters, v. 173, p. 171-181. Geobiology 27: New York, NY, G. P., and Schrag, D. P., 1998, A Neo- Li, Z.-X., Li, X.-H., Li, W.-X., and Ding, S., Springer, p. 231-271. proterozoic Snowball Earth: Science, 2008a, Was Cathaysia part of Protero- Halverson, G. P., Macdonald, F. A., Strauss, v. 281, p. 1342-1346. zoic Laurentia?—new data from J. V., Smith, E. F., Cox, G. M., and Hoffman, P. F., and Schrag, D. P., 2002, Hainan Island, south China: Terra Hubert-Theou, L., 2012, Updated def- The snowball Earth hypothesis; test- Nova, v. 20, p. 154-164. inition and correlation of the lower ing the limits of global change: Terra Li, Z.-X., Zhang, L., and Powell, C. M., Fifteenmile Group in the central and Nova, v. 14, no. 3, p. 129-155. 1995, South China in Rodinia: Part of eastern Ogilvie Mountains, in MacFar- Jefferson, C. W., 1978, The Upper Protero- the missing link between Australia- lane, K. E., and Sack, P. J., eds., Yukon zoic Redstone Copper Belt, Mackenzie East Antarctica and Laurentia?: Geol- Exploration Geology 2011: White- Mountains, Northwest Territories ogy, v. 23, no. 5, p. 407-410. horse, Yukon Geological Survey, p. [Ph.D: University of Western Ontario, Li, Z. X., Bogdanova, S. V., Collins, A. S., 75-90. 445 p. Davidson, A., De Waele, B., Ernst, R. Halverson, G. P., Maloof, A. C., Schrag, D. Jefferson, C. W., and Parrish, R., 1989, Late E., Fitzsimons, I. C. W., Fuck, R. A., P., Dudas, F. O., and Hurtgen, M. T., Proterozoic stratigraphy, U/Pb zircon Gladkochub, D. P., Jacobs, J., Karl- 2007, Stratigraphy and geochemistry ages and rift tectonics, Mackenzie strom, K. E., Lu, S., Natapov, L. M., of a ca 800 Ma negative carbon iso- Mountains, northwestern Canada: Pease, V., Pisarevsky, S. A., Thrane, K., tope interval in northeastern Svalbard: Canadian Journal of Earth Sciences, v. and Vernikovsky, V., 2008b, Assembly, Chemical Geology, v. 237, p. 5-27. 26, p. 1784-1801. configuration, and break-up history of Halverson, G. P., Wade, B. P., Hurtgen, M. Jeletsky, J. A., 1962, Pre-Cretaceous Rodinia: A synthesis: Precambrian T., and Barovich, K. M., 2010, Neo- Richardson Mountains Trough—its Research, v. 160, no. 1-2, p. 179-210. proterozoic Chemostratigraphy: Pre- place in the tectonic framework of Lister, G. S., Etheridge, M. A., and cambrian Research, v. 182, no. 4, p. Arctic Canada and its bearing on some Symonds, P. A., 1986, Detachment 98

faulting and the evolution of passive lowknife, CA, NWT Geoscience 1992, Paleomagnetic evidence for continental margins: Geology, v. 14, p. Office, p. 423. rotation in the Neoproterozoic Mount 246-250. Medig, K. P., Thorkelson, D. J., and Dun- Harper volcanic complex, Ogilvie Lund, K., Aleinikoff, J. N., Evans, K. V., lop, R. L., 2010, The Proterozoic Pin- Mountains, Yukon Territory: Current and Fanning, C. M., 2003, SHRIMP guicula Group: stratigraphy, contact Research, Part E: Geological Survey of geochronology of Neoproterozoic relations, and possible correlations, in Canada Paper 92-1E, p. 1-10. Windermere Supergroup, central McFarlane, K. E., Weston, L. H., and Rainbird, R. H., 1993, The sedimentary Idaho: implications for rifting of west- Blackburn, L. R., eds., Yukon Explo- record of mantle plume uplift preced- ern Laurentia and synchroneity of ration and Geology 2009: Whitehorse, ing eruption of the Neoproterozoic Sturtian glacial deposits: Geological YT, Yukon Geological Survey, p. 265- Natkusiak flood basalt: Journal of Society of America Bulletin, v. 115, p. 278. Geology, v. 101, p. 305-318. 349-372. Mitchum, R. M., Jr., and Van Wagoner, J. Rainbird, R. H., Jefferson, C. W., and Macdonald, F. A., and Cohen, P. A., 2011, C., 1991, High-frequency sequences Young, G. M., 1996, The early Neo- The Tatonduk inlier, Alaska-Yukon and their stacking patterns: sequence proterozoic sedimentary Succession B border, in E., A., Halverson, G. P., and stratigraphic evidence for high-fre- of Northwestern Laurentia: Correla- Shields-Zhou, G., eds., The Geological quency eustatic cycles: Sedimentary tions and paleogeographic signifi- Record of Neoproterozoic Glacia- Geology, v. 70, p. 131-160. cance: Geological Society of America tions, Volume 36: London, Geological Moores, E. M., 1991, Southwest US-East Bulletin, v. 108, p. 454-470. Society of London, p. 389-396. Antarctic (SWEAT) connection: a Rainbird, R. H., McNicoll, V. J., Theriault, Macdonald, F. A., Cohen, P. A., Dudás, F. hypothesis: Geology, v. 19, p. 425-428. R. J., Heaman, L. M., Abbott, J. G., O., and Schrag, D. P., 2010a, Early Mustard, P. S., 1991, Normal faulting and Long, D. G. F., and Thorkelson, D. J., Neoproterozoic scale microfossils in alluvial-fan deposition, basal Winder- 1997, Pan-continental River System the Lower Tindir Group of Alaska mere Tectonic Assemblage, Yukon, Draining Grenville Orogen Recorded and the Yukon Territory: Geology, v. Canada: Geological Society of Ameri- by U-Pb and Sm-Nd Geochronology 38, p. 143-146. ca Bulletin, v. 103, p. 1346-1364. of Neoproterozoic Quartzarenites and Macdonald, F. A., McClelland, W. C., Mustard, P. S., and Donaldson, J. A., 1990, Mudrocks, Northwestern Canada: Schrag, D. P., and Macdonald, W. P., Paleokarst breccias, calcretes, silcretes Journal of Geology, v. 105, p. 1-17. 2009, Neoproterozoic glaciation on a and fault talus breccias at the base of Rainbird, R. H., Stern, R. A., Khudoley, A. carbonate platform margin in Arctic upper Proterozoic “Windermere” stra- K., Kropachev, A. P., Heaman, L. M., Alaska and the origin of the North ta, northern Canadian Cordillera: Jour- and Sukhorukov, V. I., 1998, U-Pb Slope subterrane: Geological Society nal of Sedimentary Petrology, v. 60, geochronology of Riphean sandstone of America Bulletin, v. 121, p. 448- no. 4, p. 525-539. and gabbro from southeast Siberia and 473. Mustard, P. S., and Roots, C. F., 1997, Rift- its bearing on the Laurentia-Siberia Macdonald, F. A., and Roots, C. F., 2010, related volcanism, sedimentation, and connection: Earth and Planetary Sci- Upper Fifteenmile Group in the tectonic setting of the Mount Harper ence Letters, v. 164, p. 409-420. Ogilvie Mountains and correlations of Group, Ogilvie Mountains, Yukon Ross, G. M., Parrish, R. R., and Winston, early Neoproterozoic strata in the Territory: Geological Survey of Cana- D., 1992, Provenance and U-Pb northern Cordillera, in MacFarlane, K. da Bulletin, v. 492, p. 0-92. geochronology of the Mesoprotero- E., Weston, L. H., and Blackburn, L. Norris, D. K., 1978, Preliminary geological zoic Belt Supergroup (northwestern R., eds., Yukon Exploration and Geol- map of the Porcupine River area, United States): implications for age of ogy 2009: Whitehorse, YT, Yukon Geological Survey of Canada Map deposition and pre-Panthalassa plate Geological Survey, p. 237-252. Sheets H6J and H6K (E1/2). reconstructions: Earth and Planetary Macdonald, F. A., Schmitz, M. D., Crowley, Norris, D. K., 1982, Geology, Ogilvie Science Letters, v. 113, p. 57-76. J. L., Roots, C. F., Jones, D. S., Maloof, River, Yukon Territory, Geological Ross, G. M., and Villeneuve, M. E., 2003, A. C., Strauss, J. V., Cohen, P. A., Survey of Canada, Map 1526A, Provenance of the Mesoproterozoic Johnston, D. T., and Schrag, D. P., 1:250,000 scale. (1.45 Ga) Belt basin (western North 2010b, Calibrating the Cryogenian: Norris, D. K., 1997, Geology and mineral America): another piece in the pre- Science, v. 327, p. 1241-1243. and hydrocarbon potential of north- Rodinia paleogeographic puzzle: Geo- Macdonald, F. A., Smith, E. F., Strauss, J. ern Yukon Territory and northwestern logical Society of America Bulletin, v. V., Cox, G. M., Halverson, G. P., and District of Mackenzie, Ottawa, Geo- 115, p. 1191-1217. Roots, C. F., 2011, Neoproterozoic logical Survey of Canada, Geological Schrag, D. P., Berner, R. A., Hoffman, P. F., and early Paleozoic correlations in the Survey of Canada, Bulletin 422, 397 and Halverson, G. P., 2002, On the western Ogilvie Moutnains, Yukon, in p.: initiation of snowball Earth: Geo- MacFarlane, K. E., Weston, L. H., and Park, J. K., and Jefferson, C. W., 1991, chemistry, Geophysics, Geosystems, v. Relf, C., eds., Yukon Exploration and Magnetic and tectonic history of the 3. Geology 2010: Whitehorse, Yukon late Proterozoic upper Little Dal and Schwab, D. L., Thorkelson, D. J., Geological Survey, p. 161-182. Coates Lake Groups of northwestern Mortensen, J. K., Creaser, R. A., and Martel, E., Turner, E. C., and Fischer, B. J., Canada: Precambrian Research, v. 52, Abbott, J. G., 2004, The Bear River 2011, Geology of the central Macken- p. 1-35. dykes (1265-1269 Ma): westward con- zie Mountains of the northern Cana- Park, J. K., Norris, D. K., and Larochelle, tinuation of the Mackenzie dyke dian Cordillera, Sewki Mountain A., 1989, Paleomagnetism and the ori- swarm into Yukon, Canada: Precam- (105P), Mount Eduni (106A), and gin of the Mackenzie Arc of north- brian Research, v. 133, no. 3-4, p. 175- northwestern Wrigley Lake (95M) western Canada: Canadian Journal of 186. map-areas, Northwest Territories, Earth Sciences, v. 26, p. 2194-2203. Sears, J. W., and Price, R. A., 2003, Tight- NWT Special Volume, Volume 1: Yel- Park, J. K., Roots, C. F., and Brunet, N., ening the Siberian connection to west- GEOSCIENCE CANADA Volume 39 2012 99

ern Laurentia: Geological Society of Turner, E. C., and Long, D. G. F., 2008, America Bulletin, v. 115, p. 943-953. Basin architecture and syndepositional Swanson-Hysell, N. L., Rose, C.V., Calmet, fault activity during deposition of the C.C., Halverson, G.P., Hurtgen, M.T., Neoproterozoic Mackenzie Mountains Maloof, A.C., 2010, Cryogenian glacia- Supergroup, Northwest Territories, tion and the onset of carbon-isotope Canada: Canadian Journal of Earth decoupling: Science, v. 328, p. 608- Sciences, v. 45, p. 1159-1184. 611. Walter, M. R., Veevers, J. J., Calver, C. R., Thompson, R. I., Mercier, B., and Roots, C. and Grey, K., 1995, Neoproterozoic F., 1987, Extension and its influence stratigraphy of the Centralian Super- on Canadian Cordilleran passive-mar- basin, Australia: Precambrian gin evolution, in Coward, M. P., Research, v. 73, p. 173-196. Dewey, J. F., and Hancock, P. L., eds., Wang, W., Zhou, M.-F., Yan, D.-P., and Li, Continental Extensional Tectonics, J.-W., 2012, Depositional age, prove- Volume 28: London, Geological Soci- nance, and tectonic setting of the ety Special Publication, p. 409-417. Neoproterozoic Sibao Group, south- Thompson, R. I., Roots, C. F., and Mus- eastern Yangtze Block, South China: tard, P. S., 1994, Geology of Dawson Precambrian Research, v. 192-195, p. map area (116B, C, northeast of Tinti- 107-124. na Trench), Geological Survey of Wang, X.-C., Li, X.-H., Li, X.-W., Li, Z.-X., Canada, Open File 2849, scale Liu, Y., Yang, Y.-H., Liang, X.-R., and 1:50,000. Tu, X.-L., 2008, The Bikou basalts in Thorkelson, D. J., 2000, Geology and min- the northwestern Yangtze block, eral occurences of the Slats Creek, South China: Remnants of 820-810 Fairchild Lake and “Dolores Creek” Ma continental flood basalts: Geologi- areas, Wernecke Mountains, Yukon cal Society of America Bulletin, v. 120, Territory (106D/16, 106C/13, no. 11/12, p. 1478-1492. 106C/14): Exploration and Geological Wang, X.-C., Li, Z.-X., Li, X.-H., Li, Q.-L., Services Division, Yukon Region, Bul- and Zhang, Q.-R., 2011, Geochemical letin 10. and Hf-Nd isotope data of Nanhua Thorkelson, D. J., Abbott, J. G., Mortensen, rift sedimentary and volcaniclastic J. K., Creaser, R. A., Villeneuve, M. E., rocks indicate a Neoproterozoic conti- McNicoll, V. J., and Layer, P. W., 2005, nental flood basalt provenance: Lithos, Early and Middle Proterozoic evolu- v. 127, p. 427-440. tion of Yukon, Canada: Canadian Wingate, M. T. D., Campbell, I. H., Comp- Journal of Earth Sciences, v. 42, p. ston, W., and Gibson, G. M., 1998, 1045-1071. Ion microprobe U-Pb ages for Neo- Thorkelson, D. J., Mortensen, J. K., Creas- proterozoic basaltic magmatism in er, R. A., Davidson, G. J., and Abbott, south-central Australia and implica- J. G., 2001a, Early Proterozoic mag- tions for the breakup of Rodinia: Pre- matism in Yukon, Canada: constraints cambrian Research, v. 87, p. 135-159. on the evolution of northwestern Young, G. M., 1977, Stratigraphic correla- Laurentia: Canadian Journal of Earth tion of upper Proterozoic rocks of Sciences, v. 38, p. 1479-1494. northwestern Canada: Canadian Jour- Thorkelson, D. J., Mortensen, J. K., David- nal of Earth Sciences, v. 14, p. 1771- son, G. J., Creaser, R. A., Perez, W. A., 1787. and Abbott, J. G., 2001b, Early Meso- Young, G. M., 1981, Upper Proterozoic proterozoic intrusive breccias in rocks of North America: A brief Yukon, Canada: the role of hydrother- review: Precambrian Research, v. 15, p. mal systems in reconstructions of 305-330. North America and Australia: Precam- Young, G. M., 1982, The late Proterozoic brian Research, v. 111, p. 31-35. Tindir Group, east-central Alaska; Tosca, N. J., Macdonald, F. A., Strauss, J. V., Evolution of a continental margin: Johnston, D. T., and Knoll, A. H., Geological Society of America Bul- 2011, Sedimentary talc in Neoprotero- letin, v. 93, p. 759-783. zoic carbonate successions: Earth and Young, G. M., Jefferson, C. W., Delaney, G. Planetary Science Letters, v. 306, p. D., and Yeo, G. M., 1979, Middle and 11-22. late Proterozoic evolution of the Turner, E. C., 2011, Stratigraphy of the northern Canadian Cordillera and Mackenzie Mountains supergroup in Shield: Geology, v. 7, p. 125-128. the Wernecke Mountains, Yukon, in MacFarlane, K. E., Weston, L. H., and Received ?? 2012 Relf, C., eds., Yukon Exploration and Accepted as revised ?? 2012 Geology 2010: Whitehorse, Yukon, Yukon Geological Survey, p. 207-231.